PZT Microactuator with Active Constraining Layers for DSA Suspension
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Solution Overview
Problem
Conventional dual stage actuated suspension designs for hard disk drives experience a loss in PZT stroke length due to bending of piezoelectric microactuators when mounted on suspensions, resulting in reduced linear movement of the read/write head.
Innovation Solution
Incorporating one or more stiff restraining layers on the PZT microactuators to control bending, which can increase the effective linear stroke distance by altering the direction of bending when actuated, thereby enhancing the stroke length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PZT microactuators are mounted on suspensions, then fine control of read/write head positioning is achieved, but bending occurs causing loss of stroke length
Solution Approach 1:
The patent applies preliminary anti-action by bonding a restraining layer to the PZT microactuator before mounting it on the suspension. This restraining layer pre-counters the bending forces that will occur during actuation, allowing the PZT to maintain its intended stroke length while still providing fine positioning control. The restraining layer is specifically designed with properties that oppose the bending deformation without interfering with the PZT's expansion and contraction movements.
2Length of moving object
If restraining layers are added to PZT microactuators, then effective stroke length increases, but device complexity increases
Solution Approach 1:
The patent employs composite materials by bonding a restraining layer made of a different material than the PZT to the PZT microactuator. This composite structure combines the piezoelectric properties of the PZT with the mechanical properties of the restraining layer material, creating a unified component that achieves both fine positioning control and extended effective stroke length without requiring separate complex mechanisms.
3Speed
If PZT microactuators are used for fine movements, then high bandwidth control is achieved, but susceptibility to vibrations increases
Solution Approach 1:
The restraining layer serves as an intermediary element between the PZT microactuator and the suspension environment. It mediates the interaction by providing mechanical support and vibration damping while allowing the PZT to perform its high-bandwidth control function. The restraining layer absorbs and dissipates vibrational energy before it can affect the PZT, thereby reducing vibration susceptibility without compromising the speed of control response.
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
The use of restraining layers increases the effective stroke length of PZT microactuators, leading to improved head positioning control loop bandwidth, reduced susceptibility to vibrations, and lower data seek times, while also providing mechanical strength to prevent cracking during manufacturing and shock events.
Implementation Method 1
A piezoelectric element, sometimes referred to simply as a PZT, is often used as the microactuator motor
Data Source
AI summary
A PZT microactuator such as for a hard disk drive has a restraining layer bonded on its side that is opposite the side on which the PZT is mounted. The restraining layer comprises a stiff and resilient material such as stainless steel. The restraining layer can cover most or all of the top of the PZT, with an electrical connection being made to the PZT where it is not covered by the restraining layer. The restraining layer reduces bending of the PZT as mounted and hence increases effective stroke length, or reverses the sign of the bending which increases the effective stroke length of the PZT even further. The restraining layer can be one or more active layers of PZT material that act in the opposite direction as the main PZT layer. The restraining layer(s) may be thinner than the main PZT layer.