Multilayer Piezoelectric Element Outer Electrode Segmentation
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Solution Overview
Problem
Existing multilayer piezoelectric elements face issues with electrode separation and cracking under high electric fields and pressures, leading to performance degradation and reduced durability, particularly in high-speed applications like vehicle injectors.
Innovation Solution
The design incorporates outer electrodes with fixed, free, and rigid parts, where the free part has expandable openings to relax stress, and the rigid part has a larger sectional area to increase current capacity, ensuring electrical connectivity and maintaining displacement characteristics over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If outer electrodes are formed on multilayer piezoelectric element to provide electrical connectivity, then electrical conductivity is improved, but electrode separation and cracking occur under high electric field and pressure leading to reduced reliability
Solution Approach 1:
The outer electrode is divided into multiple independent conductive materials positioned separately within the multilayer piezoelectric element. This segmentation prevents complete electrode failure by ensuring that cracks or separation in one conductive material do not propagate to others, thereby maintaining electrical connectivity and improving reliability under high electric field and pressure conditions.
2Reliability
If conductive materials are positioned separately from multilayer body through outer electrodes, then performance deterioration is suppressed, but current capacity is insufficient for high-speed actuator applications
Solution Approach 1:
Multiple conductive materials are combined within the outer electrode structure, each contributing to the overall current capacity. By merging several conductive paths in parallel, the total current capacity is increased to meet high-speed actuator requirements while maintaining performance stability through the distributed configuration that suppresses deterioration.
3Productivity
If piezoelectric element is used under high electric field and high pressure for long period, then large displacement is achieved, but separation and cracking occur causing breaking of outer electrodes
Solution Approach 1:
Multiple conductive materials are pre-positioned within the multilayer piezoelectric element before operation. This beforehand preparation creates redundant electrical paths that cushion against future failure. When the element operates under high electric field and pressure, if one conductive material separates or cracks, the other materials continue to conduct electricity, preventing outer electrode breaking and maintaining durability.
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 configuration enhances the durability and performance of multilayer piezoelectric elements by preventing electrode separation and maintaining displacement characteristics, even under stringent conditions, making them suitable for high-speed applications.
Implementation Method 1
piezoelectric layers made of piezoelectric materials... Applying a specified voltage to the inner electrodes in the multilayer piezoelectric element causes the displacement of each piezoelectric layer
Data Source
AI summary
A multilayer piezoelectric element has a pair of outer electrodes and a multilayer ceramic body composed of piezoelectric layers and inner electrode layers which are alternately stacked. The outer electrodes are formed on a pair of electrode connecting surfaces in the outer circumference surfaces of the multilayer ceramic body. Each outer electrode electrically connected to the inner electrode layers through connecting material is composed of a fixed part, a free part having plural expandable-openings, and a rigid part. The fixed part is electrically contacted with the connection material. A sectional area of the rigid part is rather than that of each of the fixed part and the free part in a width direction of the outer electrode. Each outer electrode has at least one part where the fixed part, the free part and the rigid part are arranged in order in the width direction.