Disk Drive Rotary Fine Actuator with Curved Compliant Members

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Solution Overview

Problem

Current microactuator designs for disk drives face challenges in providing adequate stroke and bandwidth for fine actuation while minimizing Z-offset and preventing stick-slip phenomena, which affects the performance and volumetric data density of disk drives.

Innovation Solution

A rotary fine actuator design is introduced, where piezoelectric elements are strategically positioned closer to the read head and integrated with curved compliant members, reducing the distance between the microactuator and the read head to enhance bandwidth and minimize Z-offset, and the alignment of the fine actuator axis with the dimple contact location helps reduce stick-slip motion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If piezoelectric microactuator is affixed to mounting plate or load beam extension, then stroke is increased, but bandwidth is reduced

Engineering Contradiction:

ImprovestrokeVSAvoidbandwidth

Core Design Contradiction:

Length of moving objectVSSpeed

Solution Approach 1:

The patent introduces a new component - the flexure tongue - as an intermediary structure between the microactuator and the read head. The microactuator is affixed to the flexure tongue, which serves as a mediator to transmit actuation force directly to the read head while maintaining structural integrity. This intermediary approach allows the microactuator to be positioned optimally for both stroke and bandwidth performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Length of moving object

If microactuator is disposed farther from read head, then stroke is increased, but bandwidth is reduced

Engineering Contradiction:

ImprovestrokeVSAvoidbandwidth

Core Design Contradiction:

Length of moving objectVSSpeed

Solution Approach 1:

The patent utilizes the flexure tongue as a dimensional bridge, allowing the microactuator to be positioned at an optimal distance from the read head along the flexure tongue structure. This dimensional arrangement enables the system to achieve both adequate stroke (through the flexure tongue's mechanical advantage) and adequate bandwidth (through reduced rotational inertia) simultaneously.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Speed

If microactuator is disposed on flexure tongue, then bandwidth is improved, but Z-offset increases

Engineering Contradiction:

ImprovebandwidthVSAvoidZ-offset

Core Design Contradiction:

SpeedVSDuration of action of moving object

Solution Approach 1:

The patent applies local quality by designing the flexure tongue with specific geometric characteristics at the microactuator attachment location. The flexure tongue's cross-sectional properties and thickness are optimized locally to minimize Z-offset while maintaining the bandwidth benefits of close microactuator positioning. This localized structural optimization allows the system to achieve high bandwidth without excessive Z-offset.

Inventive Principle:

Principle #3Local quality

4Speed

If microactuator is disposed on flexure tongue, then bandwidth is improved, but stick-slip phenomena occurs

Engineering Contradiction:

ImprovebandwidthVSAvoidstick-slip phenomena

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The patent addresses the stick-slip phenomenon by carefully designing the flexure tongue's geometric properties and material characteristics to minimize friction and adhesion effects. The flexure tongue's curvature and surface properties are optimized to reduce contact friction between the microactuator and the dimple, converting what would be a harmful stick-slip effect into smooth, continuous motion that enables high-bandwidth operation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 achieves improved fine actuation performance by providing both necessary stroke and bandwidth while minimizing Z-offset and stick-slip issues, thereby enhancing the overall data density and access time in disk drives.

Implementation Method 1

A rotary fine actuator design is introduced, where piezoelectric elements are strategically positioned closer to the read head

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

integrated with curved compliant members, reducing the distance between the microactuator and the read head

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS8295012B1Disk drive suspension assembly with rotary fine actuator at flexure tongue

Publication Date: 2012.10.23 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A head gimbal assembly includes a rotary fine actuator attached to the head mounting tongue. The rotary fine actuator includes a fixed portion, a head mounting platform, first and second piezoelectric elements, and first and second curved compliant members. The first piezoelectric element is bonded to the fixed portion at a first bonding surface, and to the head mounting platform at a second bonding surface. The second piezoelectric element extends between the fixed portion and the head mounting platform. The first and second curved compliant members extend between the fixed portion and the head mounting platform. A read head is bonded to a mounting surface of the head mounting platform. The first and second bonding surfaces are parallel to the mounting surface. The read head is disposed between the first and second piezoelectric elements.