Oscillating electromagnetic attraction for head-medium contact detection

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Solution Overview

Problem

Low clearance technology (LCT) head-disk systems have reduced fly height modulation, leading to reduced contact detect strength and increased wear, as existing contact detection methods rely on thermal expansion and modulation, which are limited by thermal time constants and frequency constraints, resulting in inefficient contact detection at higher frequencies.

Innovation Solution

An oscillating electromagnetic attraction is used between the recording head and medium, with a thermal sensor detecting the oscillating temperature to determine head-medium contact, allowing for higher frequency fly height modulation and reduced contact detection time, enabling faster and more reliable contact detection across the disk surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If thermal expansion and modulation methods are used for contact detection, then contact detection can be performed, but the detection frequency is limited by thermal time constants and the detection strength is reduced

Engineering Contradiction:

Improvecontact detection strengthVSAvoiddetection frequency

Core Design Contradiction:

Measurement precisionVSSpeed

Solution Approach 1:

The patent replaces the thermal expansion-based detection mechanism with an electromagnetic attraction-based mechanism. By applying an oscillating electromagnetic signal between the head and medium, the system generates oscillating electromagnetic attraction forces that directly modulate the clearance, enabling high-frequency contact detection without being constrained by thermal time constants. This substitution of the underlying physical mechanism resolves the contradiction between detection strength and detection frequency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If fly height is reduced in LCT systems, then areal density is improved, but contact detect strength is reduced and wear increases

Engineering Contradiction:

Improveareal densityVSAvoidcontact detection reliability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent changes the fundamental parameter used for contact detection from thermal expansion to electromagnetic attraction. By utilizing the oscillating electromagnetic signal to generate attraction forces that modulate clearance, the system achieves strong contact detection signals even at reduced fly heights characteristic of LCT systems. This parameter change enables simultaneous achievement of high areal density through low fly height and high contact detection reliability through electromagnetic-based detection.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If thermal expansion methods are used for contact detection, then contact detection can be achieved, but the process time is extended due to thermal time constants

Engineering Contradiction:

Improvecontact detection accuracyVSAvoidcontact detection time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent substitutes the slow thermal expansion process with a rapid electromagnetic attraction process. The oscillating electromagnetic signal generates immediate attraction forces that respond instantaneously to clearance changes, eliminating the delay imposed by thermal time constants. This substitution maintains contact detection accuracy while reducing the detection process time by up to 200-fold as stated in the patent.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables contact detection at much higher frequencies (up to 400 kHz) and reduces contact detection time by up to 200-fold, improving manufacturing efficiency and head reliability, while allowing for two-dimensional contact power mapping and increased areal density.

Implementation Method 1

The recording head has an electromagnetic attraction to a recording medium. The circuitry is configured to oscillate the electromagnetic attraction between the recording head and the recording medium.

Methodology Applied

Scientific EffectElectromagnetic attraction: Electromagnetic Induction

Implementation Method 2

The thermal sensor, located in or near the recording head, senses an oscillating temperature that is induced by the oscillating clearance

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS8995076B1Head-medium contact detection using electromagnetic attraction

Publication Date: 2015.03.31 SEAGATE TECH LLC

AI summary

An apparatus of the present disclosure generally includes a recording head, circuitry, a thermal sensor, and a detector. The recording head has an electromagnetic attraction to a recording medium. The circuitry is configured to oscillate the electromagnetic attraction between the recording head and the recording medium. The oscillating electromagnetic attraction produces a corresponding oscillating clearance between the recording head and the recording medium. The thermal sensor, located in or near the recording head, senses an oscillating temperature that is induced by the oscillating clearance and produces a sensor signal that is representative of the sensed temperature. The detector is coupled to the thermal sensor and is configured to detect at least one of head-medium contact and clearance using the sensor signal and the electromagnetic attraction.