Disk Drive Head Scheduled Load to Shear Lubricant

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Solution Overview

Problem

Lubricant buildup on disk drive heads during extended parking periods leads to increased head-media spacing, resulting in high fly writes and longer time-to-ready issues when the heads are loaded back onto the disk.

Innovation Solution

Implementing a scheduled load and unload procedure to measure and shear off migrated lubricant from the pole area of the head, using a servo control system to adjust the time constant based on environmental conditions and measurement feedback to maintain optimal head-media spacing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the head is parked on the ramp for an extended period to save power and reduce activity, then energy consumption is reduced, but lubricant migrates from pooling areas back onto the air bearing system and pole tip, causing head-media spacing changes and high fly writes

Engineering Contradiction:

Improveenergy consumptionVSAvoidhead-media spacing stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The system performs a preliminary load operation after the head has been parked for an extended period. This preliminary action shears off the migrated lubricant from the pole tip before normal operations resume, preventing the lubricant from causing head-media spacing changes and high fly writes during subsequent operations

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system monitors head-media spacing measurements and uses this feedback to determine when lubricant migration has occurred. Based on this feedback, the system automatically triggers a scheduled load operation to shear off the migrated lubricant, maintaining reliable head-media spacing without requiring continuous monitoring or intervention

Inventive Principle:

Principle #23Feedback

2Loss of time

If the head remains parked for extended periods to reduce time-to-ready, then availability is improved, but lubricant buildup on the pole tip increases, resulting in high fly writes and longer time-to-ready when loaded

Engineering Contradiction:

Improvetime-to-readyVSAvoidlubricant buildup

Core Design Contradiction:

Loss of timeVSObject-generated harmful factors

Solution Approach 1:

The system implements periodic load operations at scheduled intervals regardless of whether the head has been parked. This periodic action prevents lubricant buildup on the pole tip by shearing it off before it can accumulate to problematic levels, ensuring that when the head is loaded for actual operations, no high fly writes occur and time-to-ready remains minimized

Inventive Principle:

Principle #19Periodic action

3Device complexity

If conventional heads are used without scheduled load operations, then device complexity is reduced, but high fly writes occur due to lubricant migration after extended parking periods

Engineering Contradiction:

Improvecontrol procedure complexityVSAvoidwrite operation reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The system uses its own operational capabilities to service itself by performing scheduled load operations that shear off migrated lubricant. The same actuator and read/write mechanisms used for normal operations are utilized to perform the cleaning function, eliminating the need for additional specialized components or complex external servicing mechanisms

Inventive Principle:

Principle #25Self-service

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 reduces the time-to-ready for disk drives and prevents high fly writes by ensuring consistent head-media spacing, even after extended parking periods, by periodically loading the head to remove excess lubricant and adjusting the time constant for varying conditions.

Implementation Method 1

An air bearing forms between the head and the disk due to the disk media rotating at high speeds

Methodology Applied

Scientific EffectAir bearing: Air Lubrication

Implementation Method 2

a heater which controls fly height through thermal expansion

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

or a piezoelectric (PZT) actuator

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS9064542B1Scheduled load of heads to reduce lubricant migration on pole tip and decrease time to ready

Publication Date: 2015.06.23 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A disk drive includes: a disk, a head, and control circuitry including a servo control system operable to actuate the head. The head is unloaded onto a ramp for a period of time based on a time constant. The head is loaded onto the disk after the period of time has elapsed and head-media spacing (HMS) is repeatedly measured. The head is unloaded when the HMS measurements become constant within a predetermined range.