Harmonic Shaping of Spindle Motor Magnetic Profile
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Solution Overview
Problem
In magnetic recording media, such as hard disk storage devices, acoustic pure tones generated by spindle motors can degrade performance by causing resonant frequencies, and reducing motor force to mitigate this also reduces the number of disks that can be rotated due to decreased torque.
Innovation Solution
A magnet and magnetizer combination with a magnetic profile is designed to superimpose specific harmonics, altering the magnetic profile to reduce acoustic pure tones at specific frequencies without significantly impacting torque, thereby maintaining the number of disks that can be rotated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the overall force generated by the motor is reduced to reduce acoustic pure tones, then acoustic performance is improved, but the torque that rotates the disks is reduced
Solution Approach 1:
The patent applies local quality by modifying specific portions of the magnetic profile rather than uniformly reducing the entire magnetic field. By adding harmonic components at specific locations in the magnetic profile (e.g., at pole transitions), the invention selectively reduces acoustic pure tones at problematic frequencies while preserving the overall torque-generating force of the motor.
Solution Approach 2:
The patent changes the parameters of the magnetic profile by superimposing harmonic components with specific frequencies and amplitudes. This modifies the magnetic field characteristics to reduce acoustic resonance at particular frequencies while maintaining the integral force required for disk rotation. The harmonic shaping adjusts the magnetic flux distribution without significantly altering the total force output.
2Object-affected harmful factors
If the magnetic profile is altered to reduce acoustic pure tones, then acoustic performance is improved, but the complexity of the motor design increases
Solution Approach 1:
The patent applies preliminary action by incorporating the harmonic shaping directly into the magnetization process of the motor magnets. The desired harmonic profile is established during manufacturing through controlled magnetization techniques, rather than requiring complex active control systems or additional components during operation. This upfront design approach reduces acoustic issues without adding operational complexity.
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 effectively reduces acoustic pure tones at specific frequencies, enhancing acoustic performance by shaping the magnetic profile of the motor's magnetic components, thus improving hard drive efficiency without compromising torque.
Implementation Method 1
A magnet and magnetizer combination with a magnetic profile is designed to superimpose specific harmonics
Implementation Method 2
The rotation generates an acoustic pure tone at a particular frequency
Implementation Method 3
The rotation generates an acoustic pure tone at a particular frequency
Data Source
AI summary
A device includes a magnet and a magnetizer. The magnetizer is operable to rotate with respect to the magnet. The rotation generates an acoustic pure tone at a particular frequency. A combination of the magnet and the magnetizer has a magnetic profile. The combination is altered to superimpose a particular harmonic shape on the magnetic profile to reduce the acoustic pure tone at the particular frequency.