Preheating Hard Disk Drive Head Slider for Switch Seek
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Solution Overview
Problem
In hard disk drives, the delay associated with thermal flying height control (TFC) heater element time constant leads to performance issues during head switching, as only one head slider is heated at a time, causing a delay in the preparation of the switched-to head for immediate operation.
Innovation Solution
Pre-heating the switched-to head slider while the active head is still performing a read or write operation, allowing both heads to be heated simultaneously and minimizing the delay associated with the TFC heater element time constant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If only one head slider is heated at a time using TFC heater element, then the flying height control is achieved for the active head, but the switched-to head experiences delay in preparation for immediate operation
Solution Approach 1:
The patent applies preliminary action by pre-heating the switched-to head slider before the head switch occurs. The system identifies which head will be switched to next and applies TFC heater power to that head in advance, so that when the switch occurs, the head is already at the required temperature and flying height, eliminating the delay associated with heating during the switch.
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that while one head is actively being heated during its operation, the next head to be switched to is simultaneously being prepared in advance. This overlapping heating approach ensures that heating actions are continuous across head switches, preventing idle time where no head is properly prepared.
2Speed
If TFC heater element time constant is reduced for faster head switching, then the head switching delay is minimized, but the flying height control precision deteriorates
Solution Approach 1:
By performing the heating action in advance during the previous head's operation, the system allows the full TFC heater time constant to work without compression. The switched-to head is gradually heated to the target temperature before switching, ensuring precise flying height control while achieving fast switching because the preparation work was done beforehand.
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 the switched-to head to begin its operation immediately after switching, reducing the delay and enhancing HDD performance by allowing simultaneous heating of both heads, thus avoiding the TFC power regime limitations of conventional methods.
Implementation Method 1
By applying current to the heater, the surrounding slider material is caused to expand in response to the heat, which causes a bulge in the slider toward the disk thus reducing the flying height of the read-write head
Implementation Method 2
By applying current to the heater, the surrounding slider material is caused to expand in response to the heat
Data Source
AI summary
Managing the flying height of a read-write head slider, such as in the context of a short or head switch seek, involves pre-heating the switched-to head while the active head is still performing a data read or write operation. Thus, both the active head and the switched-to head may be heated simultaneously, and once the switched-to head is switched to an active state upon the active head completing its corresponding operation, the switched-to head can immediately begin its operation with minimal or no further delay.