Piezoelectric Actuator Electrode Design for Stress Relaxation
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Solution Overview
Problem
Conventional piezoelectric actuators for ink jet heads face issues with increased complexity and reduced deformation due to compressive stress from mismatched coefficients of linear expansion between piezoelectric layers and joining members, requiring multiple terminals and wiring lines for voltage application.
Innovation Solution
A piezoelectric actuator design featuring a piezoelectric layer with a lower coefficient of linear expansion than the joining member, a first electrode, a second electrode in conduction with the first electrode, and a low dielectric layer between the second electrode and the piezoelectric layer, allowing for reduced compressive stress relaxation and simplified voltage application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a second electrode is added to surround the first electrode for relaxing compressive stress, then the compressive stress is relaxed and deformation efficiency is improved, but the number of terminals and wiring lines increases and device complexity increases
Solution Approach 1:
The patent merges the first electrode and second electrode into a single integrated electrode structure. The electrode has a first region corresponding to the first electrode and a second region surrounding the first region corresponding to the second electrode, both formed as one continuous conductive layer. This eliminates the need for separate terminals and wiring lines for both electrodes, reducing device complexity while maintaining the stress-relaxation function through the polarized second region.
Solution Approach 2:
The integrated electrode serves multiple functions: the first region applies electric fields for piezoelectric deformation, while the second region relaxes compressive stress through polarization. Additionally, the insulating film between the electrode and piezoelectric layer serves dual purposes as both electrical insulation and mechanical stress management. This multi-functionality reduces the overall component count and simplifies the device structure.
2Manufacturing precision
If a low dielectric layer is added between the second electrode and piezoelectric layer to concentrate voltage, then voltage is concentrated on the low dielectric layer and compressive stress relaxation is improved, but device complexity increases
Solution Approach 1:
The insulating film is merged with the electrode structure formation process, being formed simultaneously or in close sequence with the electrode layers. This integration reduces the number of discrete manufacturing steps and simplifies the overall device architecture while maintaining the voltage concentration effect through the low dielectric constant material positioned between the electrode and piezoelectric layer.
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 design mitigates compressive stress, maintains deformation efficiency, and reduces the need for multiple terminals and wiring lines by concentrating voltage on the low dielectric layer during driving, while allowing polarization of both portions during polarization.
Implementation Method 1
a piezoelectric actuator, which drives an object when an electric field is applied thereto to generate piezoelectric deformation of the piezoelectric actuator
Implementation Method 2
a low dielectric layer which is formed between the piezoelectric layer and the second electrode and which has a dielectric constant lower than a dielectric constant of the piezoelectric layer
Implementation Method 3
the compressive stress in the in-plane direction remains in the piezoelectric layer, due to the difference in the coefficient of linear expansion between the both
Data Source
AI summary
A piezoelectric actuator is provided, including a piezoelectric layer which is joined to a joining member and which has a coefficient of linear expansion smaller than a coefficient of linear expansion of the joining member; a first electrode which is arranged on one surface of the piezoelectric layer; a second electrode which is arranged on a portion of the one surface of the piezoelectric layer different from the first electrode and which is in conduction with the first electrode; and a low dielectric layer which is formed between the piezoelectric layer and the second electrode and which has a dielectric constant lower than a dielectric constant of the piezoelectric layer.