Magnetic Disk Device Voltage Control for Assist Element Reliability

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Solution Overview

Problem

In magnetic disk devices, disturbance vibrations lead to inferior servo-positioning quality, resulting in increased write-retry frequency and accelerated deterioration of assist elements like STO elements due to prolonged voltage application, which increases failure rates.

Innovation Solution

A magnetic disk device with a voltage control system that adjusts the bias voltage applied to assist elements based on positional error data, reducing the voltage when disturbance vibrations occur to prevent excessive stress and failure, and incorporating a thermal assist section using an optical element for data writing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If voltage is continuously applied to the assist element during write operations, then data recording is assisted effectively, but the assist element deteriorates faster and failure rate increases

Engineering Contradiction:

Improveassist element reliabilityVSAvoidvoltage application duration

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent applies dynamics by making the voltage application to the assist element conditional and variable rather than continuous and fixed. The voltage control section dynamically adjusts whether to apply voltage based on real-time servo positioning quality assessment, switching between voltage application and non-application states to optimize both recording assistance and element reliability

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of voltage application from a constant state to a variable state based on servo positioning quality. By monitoring positional error data and write retry frequency, the system adjusts the voltage application parameter (from applied to not applied) to prevent assist element deterioration while maintaining effective data recording when needed

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If write retry frequency increases due to disturbance vibration, then data recording accuracy is maintained, but assist element deterioration is accelerated

Engineering Contradiction:

Improvedata recording accuracyVSAvoidassist element reliability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent implements feedback by continuously monitoring servo positioning quality indicators (positional error data and write retry frequency) and using this information to control voltage application to the assist element. The voltage control section receives feedback about positioning quality and adjusts voltage application accordingly, creating a closed-loop system that balances recording accuracy with element protection

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies preliminary anti-action by proactively reducing voltage application to the assist element when disturbance vibrations are detected (indicated by increased write retry frequency). Instead of waiting for element failure, the system preemptively reduces stress on the assist element when positioning quality deteriorates, preventing further deterioration before it causes failure

Inventive Principle:

Principle #9Preliminary anti-action

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 solution effectively reduces the failure rate of assist elements by optimizing voltage application during disturbance vibrations, maintaining the reliability and longevity of the STO and optical elements, thereby enhancing the overall performance and durability of the magnetic disk device.

Implementation Method 1

an assist section configured to assist, when the magnetic head writes data on the magnetic disk, write of the data by utilizing an assist element

Methodology Applied

Scientific EffectSpin-torque oscillation:

Implementation Method 2

incorporating a thermal assist section using an optical element for data writing

Methodology Applied

Scientific EffectOptical heating:

Data Source

PatentUS11404084B2Magnetic disk device

Publication Date: 2022.08.02 KK TOSHIBA

AI summary

According to one embodiment, a magnetic disk device includes a magnetic disk, a magnetic head configured to write data on the magnetic disk, an assist section configured to assist, when the magnetic head writes data on the magnetic disk, write of the data by utilizing an assist element, a voltage control section configured to control a voltage to be applied to the assist element, and a positioning control section configured to carry out positioning of the magnetic head relatively to the magnetic disk on the basis of servo data and acquire positional error data of the magnetic head positioned on the basis of the servo data. The voltage control section adjusts the voltage to be applied to the assist element on the basis of the positional error data.