Multi-layer Piezoelectric Element Asymmetric Electrode Spacing
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Solution Overview
Problem
Multi-layer piezoelectric elements experience separation of external electrode plates due to thermal expansion differences between active and inactive sections, leading to reduced durability and stability during operation.
Innovation Solution
A multi-layer piezoelectric element design with wider spacing and thicker electrically-conductive bonding material between inactive sections and the external electrode plate, compared to the active section, to manage heat dissipation and reduce thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrically-conductive bonding material is placed near the boundary between the active section and inactive section, then electrical connection is achieved, but the bonding material becomes cracked or comes unstuck due to thermal expansion differences
Solution Approach 1:
The patent applies different spacing distances between the external electrode plate and the stacked body at different locations. Specifically, the first spacing distance at the boundary between active and inactive sections is larger than the second spacing distance at other locations. This local variation in spacing reduces thermal expansion stress concentration at the critical boundary area, preventing bonding material failure while maintaining electrical connection reliability.
Solution Approach 2:
The patent introduces a larger first spacing distance at the boundary area before thermal expansion occurs, creating a buffer zone that accommodates thermal expansion differences between the active and inactive sections. This pre-established cushioning space prevents the bonding material from being subjected to excessive stress during operation, thereby preventing cracking or debonding.
2Use of energy by moving object
If heat is accumulated in the stacked body during driving operation, then self-heating phenomenon occurs, but the bonding material may become cracked or come unstuck
Solution Approach 1:
The patent implements location-specific spacing design where the first spacing distance at the thermal stress-prone boundary area is larger than the second spacing distance at other areas. This local quality differentiation allows the boundary region to better accommodate thermal expansion during self-heating, maintaining bonding material integrity while allowing the device to operate with inherent self-heating characteristics.
3Temperature
If the active section has greater thermal expansion than the inactive section, then thermal expansion difference causes bonding material failure, but uniform spacing cannot accommodate this difference
Solution Approach 1:
The patent directly addresses the thermal expansion difference by implementing non-uniform spacing: the first spacing distance at the boundary between active and inactive sections is specifically made larger than the second spacing distance at other locations. This local quality approach allows each region to accommodate its thermal expansion characteristics, with the larger spacing at the boundary absorbing the differential expansion between active and inactive sections.
Solution Approach 2:
The patent employs asymmetric spacing design where the distance between the external electrode plate and the stacked body varies by location. The first spacing distance at the thermal expansion boundary is asymmetrically larger than the second spacing distance at other areas, creating an asymmetric structure that naturally accommodates the asymmetric thermal expansion behavior between active and inactive sections.
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 enhances the long-term durability and stability of the multi-layer piezoelectric element by preventing external electrode plate separation and ensuring consistent performance over time.
Implementation Method 1
heat is accumulated due to a self-heating phenomenon which occurs in the stacked body 6 during driving operation
Implementation Method 2
the active section 4 including the internal electrode layer 3 is greater in thermal expansion than the inactive section 5 free from the internal electrode layer 3
Data Source
AI summary
A multi-layer piezoelectric element includes: a stacked body comprising an active section, and inactive sections disposed at opposite ends in a stacking direction of the active section; an electrically-conductive bonding material disposed on a side surface of the stacked body from the active section to the inactive sections; and an external electrode plate attached, through the electrically-conductive bonding material, to the side surface of the stacked body, a spacing between a side surface of at least one of the inactive sections and the external electrode plate being wider than a spacing between a side surface of the active section and the external electrode plate, and the electrically-conductive bonding material situated between the side surface of at least one of the inactive sections and the external electrode plate being larger in thickness than the electrically-conductive bonding material situated between the side surface of the active section and the external electrode plate.