Linear Actuator Coil Segmentation for Resonance Control

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Solution Overview

Problem

Conventional linear actuators in data storage devices suffer from out-of-plane resonant vibrations due to broad mass distribution, which leads to instability and performance issues, and flexible printed circuits (FPCs) contribute to asymmetrical mass and fatigue failure.

Innovation Solution

A linear actuator design featuring an electrically conductive coil with parts wound in the same rotary direction about an axis, coupled with a dual pole magnet assembly, where the magnet is linearly movable, reducing out-of-plane resonances and eliminating the need for FPCs by fixing the coil to a housing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If a conventional linear actuator uses a coil with significant mass broadly distributed about the actuation axis, then the coil can provide sufficient electromagnetic force, but out-of-plane resonant vibrations occur leading to instability and bandwidth reductions

Engineering Contradiction:

Improveelectromagnetic forceVSAvoidout-of-plane resonant vibrations

Core Design Contradiction:

ForceVSStability of the object's composition

Solution Approach 1:

The coil is divided into two separate coil portions (first and second portions) that are positioned on opposite sides of the actuation axis. Each portion has reduced mass compared to a conventional single coil, and their combined mass distribution is more narrowly concentrated about the actuation axis, reducing out-of-plane resonant vibrations while maintaining electromagnetic force generation capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The two coil portions are positioned asymmetrically on opposite sides of the actuation axis and carry currents in opposite directions. This asymmetric arrangement with opposing currents creates a balanced electromagnetic force system that generates linear actuation force while minimizing rotational moments and out-of-plane vibrations

Inventive Principle:

Principle #4Asymmetry

2Ease of operation

If a flexible printed circuit (FPC) is used to energize the moving coil, then electrical connection is achieved, but asymmetrical mass distribution results and fatigue failure occurs due to repeated cycling

Engineering Contradiction:

Improveelectrical connectionVSAvoidfatigue failure

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The FPC is completely removed from the system. Instead of using an FPC to energize the moving coil, the patent uses two stationary coil portions with opposing current directions that are electrically connected through stationary leads, eliminating the moving electrical connection and associated FPC-related problems

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of having a moving coil energized by a flexible circuit, the patent inverts the approach by using stationary coil portions that are fixed to the housing. The electrical connection is made through stationary leads rather than a flexible printed circuit, reversing the traditional voice coil actuator architecture

Inventive Principle:

Principle #13The other way round (Inversion)

3Force

If the coil mass is broadly distributed about the actuation axis, then electromagnetic force is sufficient, but the mass distribution causes out-of-plane resonances and instability

Engineering Contradiction:

Improveelectromagnetic forceVSAvoidmass distribution

Core Design Contradiction:

ForceVSWeight of moving object

Solution Approach 1:

The coil mass is segmented into two separate portions positioned on opposite sides of the actuation axis. Each portion has reduced individual mass, and the combined mass distribution is more narrowly concentrated about the actuation axis, reducing the moment of inertia and out-of-plane resonant vibrations while maintaining sufficient electromagnetic force through the opposing current configuration

Inventive Principle:

Principle #1Segmentation

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 reduces out-of-plane resonances, simplifies manufacturing, and eliminates fatigue failures and asymmetrical effects, providing more stable and efficient linear movement of recording heads in data storage mechanisms.

Implementation Method 1

Transmission of an electric current through the first part of the electrically conductive coil in a first current flow direction about the axis and through the second part of the electrically conductive coil in an opposite second current flow direction about the axis induces linear movement of the magnet relative to the electrically conductive coil

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Data Source

PatentUS10097075B2Linear actuator with coil winding portions having opposing current flow directions

Publication Date: 2018.10.09 ORACLE INT CORP

AI summary

A linear actuator for linearly positioning a recording head in a data storage mechanism. The disclosed linear actuator includes an electrically conductive coil having first and second parts that are both wound in the same rotary direction about an axis, and a magnet spaced from the electrically conductive coil by an air gap. Transmission of an electric current through the first part of the electrically conductive coil in a first current flow direction about the axis and through the second part of the electrically conductive coil in an opposite second current flow direction about the axis induces linear movement of one of the electrically conductive coil and magnet relative to the other of the electrically conductive coil and magnet.