Magnetic Disk Thermal Sensing for Head Collision Prevention
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Solution Overview
Problem
Magnetic heads in disk devices collide with microscopic projections on the recording medium surface during operation, leading to damage and hindering effective recording and reproduction due to manufacturing defects like projections and recesses.
Innovation Solution
Incorporating a thermal resistance sensor with a wider width than the recording and read heads, allowing simultaneous inspection of multiple tracks for surface defects, and setting record-prohibited tracks to prevent collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the magnetic head moves with a minute gap of 1 nm to improve recording density, then linear recording density is improved, but the magnetic head collides with microscopic projections on the recording surface causing damage
Solution Approach 1:
The patent applies preliminary action by detecting surface defects (projections and recesses) on the recording medium before normal recording operations begin. The magnetic head performs a preliminary scan to identify defective areas, and the controller stores this information to avoid these areas during subsequent recording and reproduction operations, thereby preventing head damage while maintaining high recording density
Solution Approach 2:
The patent introduces an intermediary detection mechanism between the magnetic head and the recording surface. A separate detection process using thermal resistance sensors or other detection means identifies surface defects, and this information is transmitted to the controller which then adjusts head positioning to avoid defective areas, acting as an intermediary layer that protects the head from direct contact with projections
2Measurement precision
If conventional defect inspection methods are used to detect surface defects, then defect detection is possible, but inspection time is excessively long
Solution Approach 1:
The patent merges the defect detection function with the existing magnetic head structure by integrating thermal resistance sensors or using the magnetic head itself for detection. This combination allows defect inspection to be performed using the same hardware infrastructure already present in the disk device, eliminating the need for separate inspection equipment and reducing inspection time while maintaining detection accuracy
Solution Approach 2:
The patent replaces conventional mechanical or contact-based inspection methods with thermal resistance sensing or magnetic field-based detection. These non-contact detection methods use thermal or magnetic fields instead of physical contact, enabling faster inspection speeds without compromising defect detection accuracy, thereby significantly reducing inspection time
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
Reduces defect inspection time significantly, preventing magnetic head damage and enhancing the reliability of magnetic disk devices by accurately identifying and avoiding defective areas.
Implementation Method 1
a thermal resistance sensor having a third width in a direction intersecting the recording tracks, which is wider than the first width and the second width, and detecting a surface condition of the recording medium
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a rotatable recording medium including concentric recording tracks, a magnetic head including a recording element having a first width, a reproducing element having a second width, and a thermal resistance sensor having a third width wider than the first width and the second width, a head actuator that positions the magnetic head on any recording track, a detection circuit that detects defects on a surface of the recording medium based on a sensor output of the thermal resistance sensor, and a controller that, when inspecting the surface condition of the recording medium by the thermal resistance sensor, sets a feed pitch of the magnetic head to within ½ of the third width and three or more recording tracks.