Stacked D33 PZT Microactuator with Constraint Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing disk drive suspensions face limitations in achieving precise positioning and high servo bandwidth due to the constraints of traditional microactuators, particularly in dual-stage actuated systems where the actuator's effectiveness is hindered by the need for larger structures to maintain stroke length and resist mechanical stress.
Innovation Solution
A PZT microactuator with a stacked d33 mode construction and a stiff constraint layer is used, which expands or contracts longitudinally when an electric field is applied, increasing the effective stroke length and reducing the device's mass while enhancing shock tolerance by opposing expansion or contraction, thus allowing for more precise positioning and higher servo bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If traditional d31 mode PZT actuators are used, then the actuator structure can be simpler, but the stroke length per unit voltage is limited and device mass is higher
Solution Approach 1:
The patent changes the piezoelectric mode from d31 to d33, which fundamentally alters the strain-voltage relationship. The d33 mode provides approximately twice the stroke length per unit voltage compared to d31 mode, directly resolving the contradiction by improving stroke length while allowing for reduced actuator mass and size.
Solution Approach 2:
The patent employs a composite structure combining PZT piezoelectric material with a constraint layer. This composite construction enables the d33 mode actuator to achieve enhanced stroke length while the constraint layer provides mechanical support, allowing for a more compact and lighter design compared to traditional d31 mode actuators.
2Productivity
If larger actuator structures are used to maintain stroke length, then stroke length is preserved, but the suspension mass increases and servo bandwidth decreases
Solution Approach 1:
By switching to d33 mode operation, the patent achieves higher stroke length per unit voltage, which allows for a smaller, lighter actuator structure to provide the same positioning capability. This mass reduction directly improves servo bandwidth, resolving the contradiction between productivity and weight.
3Reliability
If constraint layer is added to oppose expansion, then shock tolerance is enhanced, but device complexity increases
Solution Approach 1:
The constraint layer is integrated as part of the composite actuator structure, bonding the PZT element to the constraint layer in a unified construction. This integration approach provides shock tolerance enhancement while minimizing additional complexity, as the constraint layer serves multiple functions including mechanical support and stress distribution.
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 PZT microactuator with a constraint layer achieves approximately twice the stroke length per unit of input voltage compared to traditional d31 mode actuators, reducing the overall size and mass of the suspension, leading to improved servo bandwidth and shock tolerance, while maintaining or increasing stroke sensitivity.
Implementation Method 1
A commonly used piezoelectric material is lead zirconate titanate (PZT), although other piezoelectric materials are also used and known. In the discussion and claims that follows, for simplicity the piezoelectric device that is the microactuator will sometimes be referred to simply as a 'PZT' for shorthand
Implementation Method 2
The microactuator has a stiff constraint layer or constraining layer adhesively bonded to it, or formed integrally with it, on the side of the microactuator that is opposite the side that is mounted to the suspension. The stiff constraint layer tends to oppose expansion or contraction of the PZT, which actually increases the effective stroke length of the device.
Data Source
AI summary
A microactuator for a dual stage actuated suspension for a hard disk drive is constructed as a longitudinal stack of piezoelectric (PZT) elements acting in the d33 mode, expanding or contracting longitudinally when an electric field is applied across them in the longitudinal direction. The microactuator has interlaced electrode fingers that separate and define the individual PZT elements, and apply the electric field. A stiff constraint layer having a high Young's modulus is affixed to the microactuator on the side opposite the suspension to which the microactuator is bonded. The constraint layer may be a layer of substantially inactive PZT material that is formed integrally with the PZT elements but without electrodes in the inactive PZT layer. The presence of the stiff constraint layer increases the effective stroke length of the microactuator.