Magnetic Disk Microactuator Bias Voltage Switching
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Solution Overview
Problem
In magnetic disk devices, the continuous application of bias voltage can lead to a short circuit due to the migration of silver paste conductive adhesive between the positive and negative electrodes of piezoelectric elements, especially in biased driving methods, which may depolarize the elements and reduce the device's reliability.
Innovation Solution
A magnetic disk device with a controller that switches the bias voltage and drive voltage based on the operation state, applying a reduced bias voltage and narrower drive voltage range during relaxation operations to prevent excessive reverse bias and adhesive migration, thereby maintaining the stability and reliability of the piezoelectric elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bias voltage is continuously applied to piezoelectric elements in biased driving method, then the piezoelectric elements can be driven in push-pull method preventing reverse voltage depolarization, but the conductive adhesive may migrate between electrodes causing short circuit
Solution Approach 1:
The patent applies periodic switching between biased driving and single-ended driving modes. During biased driving, push-pull operation prevents depolarization. During single-ended driving, reverse voltage is avoided. This periodic alternation resolves the contradiction by ensuring neither depolarization nor adhesive migration occurs continuously
Solution Approach 2:
The patent dynamically switches between two driving modes (biased driving and single-ended driving) based on operational requirements. This dynamic approach allows the system to adaptively prevent both depolarization and conductive adhesive migration, resolving the technical contradiction through flexible control
2Device complexity
If single-ended driving is used with one drive voltage around 0 V, then the drive circuit is simplified, but reverse voltage may be applied causing depolarization of piezoelectric elements
Solution Approach 1:
The patent dynamically switches between single-ended driving (simpler circuit) and biased driving (more reliable polarization) modes. This dynamic switching resolves the contradiction by using the simpler circuit when possible while protecting polarization stability when needed
Solution Approach 2:
The patent periodically alternates between single-ended and biased driving modes, ensuring that the piezoelectric elements are protected from continuous reverse voltage exposure while still benefiting from the simplified circuit architecture of single-ended driving during safe operational periods
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 reduces the risk of short circuits and depolarization, enhancing the reliability and performance of the magnetic disk device by controlling voltage levels according to operational states, especially during relaxation operations.
Implementation Method 1
a microactuator that is mounted on the actuator and finely swings the head in a radial direction of the disk by a piezoelectric element that extends and contracts when a drive voltage based on a bias voltage is applied to the piezoelectric element
Data Source
AI summary
According to one embodiment, a magnetic disk device including a disk, a head that writes data to the disk and reads data from the disk, an actuator that is rotationally driven and controls movement of the head mounted above the disk, a microactuator that is mounted on the actuator and finely swings the head in a radial direction of the disk by a piezoelectric element that extends and contracts when a drive voltage based on a bias voltage is applied to the piezoelectric element, and a controller that switches the bias voltage according to an operation state during an access process.