Integrated Touchdown Sensors for Hard Disk Drive Heads
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Solution Overview
Problem
Conventional touchdown detection methods in disk drives are inadequate as they do not effectively detect prolonged contact between the head and magnetic media, leading to potential drive failure and require a unified technique for calibration and operation.
Innovation Solution
Integration of dual thermal sensors, one proximate and one distal to the air-bearing surface, to detect temperature differences caused by frictional heating during touchdown, allowing for precise detection of contact and maintaining optimal spacing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional touchdown detection methods (disk slow down, readout channel noise, strain gauges, acoustic emission) are used, then touchdown can be detected in some conditions, but no single technique works across all media radii and detection accuracy is insufficient
Solution Approach 1:
The head is divided into multiple thermal sensors positioned at different locations (proximate to ABS and distal from ABS). Each sensor monitors temperature changes in its specific region, allowing the system to detect touchdown events across different media radii and positions, thereby improving both detection accuracy and adaptability.
Solution Approach 2:
The patent replaces conventional mechanical and acoustic detection methods (strain gauges, acoustic emission) with a thermal-based detection system. By measuring temperature changes caused by frictional heating during touchdown, the system achieves more reliable and versatile detection that works across all media radii without relying on mechanical contact or acoustic signals.
2Reliability
If prolonged contact between head and disk is allowed, then calibration can be performed, but contact time should be limited to prevent drive failure
Solution Approach 1:
The thermal sensors provide real-time feedback on temperature changes that indicate touchdown events. When prolonged contact is detected through temperature monitoring, the system can immediately respond by adjusting the thermal actuator to reduce contact time, thereby preventing drive failure while maintaining necessary calibration operations.
Solution Approach 2:
The thermal sensors are positioned and configured in advance to detect the onset of touchdown before prolonged contact occurs. This allows the control system to take preliminary action to limit contact duration, preventing the harmful effects of extended contact while still permitting necessary calibration touchdown events.
3Reliability
If thermal actuator heating is increased to ensure head-media contact, then touchdown can be achieved, but excessive heat may cause unintended consequences
Solution Approach 1:
The patent employs multiple thermal sensors at different locations within the head structure (proximate to ABS and distal from ABS) to create localized temperature monitoring. This allows precise control of heating in specific regions to achieve touchdown without excessively heating the entire head, thereby improving touchdown reliability while controlling overall temperature.
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
Enhances touchdown detection accuracy, reducing drive failure risks and enabling improved calibration and operation by maintaining a controlled fly height, thus improving disk drive performance and reliability.
Implementation Method 1
detect temperature differences caused by frictional heating during touchdown
Implementation Method 2
Heat generated by the thermal actuator causes local thermal expansion of the head, which locally reduces the spacing between the head and magnetic media
Data Source
AI summary
A method and system for providing a disk drive is described. The disk drive includes media such as one or more disks, a slider, and a head residing on the slider. The head has an air-bearing surface (ABS), a portion of which contacts the media during touchdown. The head further includes a plurality of touchdown sensors. A first touchdown sensor is proximate to the ABS, while a second touchdown sensor is distal from the ABS. The touchdown sensors are capable of detecting a temperature change of 0.1 degree Celsius or, in some embodiments, smaller.