Piezoelectric Actuator Stress Relieving Layer Design
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Solution Overview
Problem
Piezoelectric actuator units face challenges in maintaining durability and consistent displacement under high voltage and pressure over long periods, with existing stress relieving layers not adequately addressing the issue of crack growth and short-circuiting.
Innovation Solution
A multi-layer piezoelectric actuator unit with a stress relieving layer composed of scattered partial metal layers and voids, where a peel-off section is formed at the interface with the piezoelectric layer, dispersing stress and preventing crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a multi-layer piezoelectric element with partial electrode structure is used, then the layer thickness can be made smaller and manufacturing cost reduced, but stress concentrates at the interface between active and inactive regions causing crack growth
Solution Approach 1:
The metal layer is segmented into a first metal layer and a second metal layer separated by an insulating layer, creating a multi-layered electrode structure that distributes stress more evenly and prevents stress concentration at single interfaces
Solution Approach 2:
An insulating layer is introduced as an intermediary between the first and second metal layers, preventing direct electrical contact while maintaining mechanical stress distribution, thus avoiding crack propagation through the piezoelectric layer
2Strength
If inactive layers are stacked on end faces to provide structural support, then the element maintains structural integrity, but stress concentrates at the interface between active and inactive layers causing crack growth
Solution Approach 1:
The metal layer is divided into multiple segments (first and second metal layers) separated by an insulating layer, distributing the stress interface across multiple locations rather than concentrating it at a single boundary with inactive layers
Solution Approach 2:
Different regions of the metal layer are differentiated into first and second metal layers with different spatial positions, allowing local stress management at different interfaces with the piezoelectric and inactive layers
3Reliability
If the piezoelectric element is housed in a constraining case, then the element is protected and positioned, but compressive stress is generated during expansion causing reduced displacement and potential failure
Solution Approach 1:
The metal layer is segmented into first and second metal layers separated by an insulating layer, creating a compliant multi-layer structure that can accommodate expansion stresses without generating excessive compressive force against the case
Solution Approach 2:
A composite structure is formed by combining metal layers with an insulating layer, creating a multi-material system that balances structural support with stress compliance, allowing controlled displacement while maintaining integrity under case constraints
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 solution effectively suppresses crack growth and maintains stable displacement over time, enhancing durability and preventing short-circuiting, allowing for continuous operation under high voltage and pressure.
Implementation Method 1
When an electric field is generated in the space between the opposing metal layers 107, the active region A expands in the direction of the electric field due to the reverse piezoelectric effect
Data Source
AI summary
A piezoelectric actuator unit which undergoes less change in the amount of displacement and shows high durability in continuous operation under a high voltage and a high pressure over a long period of time is provided.The piezoelectric actuator unit including a multi-layer piezoelectric element having piezoelectric layers and metal layers with the piezoelectric layers and the metal layers being stacked one on another, and a case which houses the multi-layer piezoelectric element, wherein at least one of the plurality of metal layers is stress relieving layer which consists of a plurality of partial metal layers that are scattered throughout the entire region between two piezoelectric layers which adjoin the partial metal layers in the direction of stacking, and voids, and a peel-off section is formed at least in a part of the interface between the stress relieving layer and the piezoelectric layer that adjoins therewith.