Chamfered Piezoelectric Electrodes for High Voltage Reliability
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Solution Overview
Problem
Acoustic generators with piezoelectric elements experience significant sound pressure decrease in the low frequency range and are prone to dielectric breakdown and breakage when used at high voltages for extended periods, particularly due to charge concentration at the corners of internal electrodes.
Innovation Solution
A piezoelectric element design featuring chamfered corner portions of internal electrodes and a conductor layer between the chamfered corners and edge portions, which disperses electric charge and stress, reducing the risk of dielectric breakdown and breakage, while maintaining high sound pressure and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the voltage applied on the acoustic generator is increased to improve sound pressure in the low frequency range, then the sound pressure is improved, but dielectric breakdown occurs in the piezoelectric layer at the corner portions of the internal electrode where electric charge is concentrated
Solution Approach 1:
The patent applies different treatments to different parts of the internal electrode: the corner portions are chamfered to reduce charge concentration, while the non-corner portions maintain their original structure. This local differentiation allows the device to handle high voltages without dielectric breakdown at critical locations while preserving overall functionality.
Solution Approach 2:
The chamfering of corner portions is performed in advance before the piezoelectric element is assembled into the acoustic generator. This preliminary treatment prevents charge concentration and potential dielectric breakdown before high voltage operation begins, cushioning against future reliability issues.
2Power
If the voltage applied on the acoustic generator is increased to improve sound pressure in the low frequency range, then the sound pressure is improved, but cracks occur in the corner portions of the internal electrode where electric charge is concentrated, causing breakage of the piezoelectric element
Solution Approach 1:
The corner portions of the internal electrode are selectively chamfered to eliminate stress concentration points, while the rest of the electrode structure remains unchanged. This localized modification prevents crack initiation at the most vulnerable locations under high voltage stress.
Solution Approach 2:
The chamfering treatment is applied beforehand to remove sharp corners that would otherwise serve as stress concentrators. This preliminary structural modification cushions against the development of cracks and subsequent breakage during high voltage operation.
3Volume of moving object
If the acoustic generator is miniaturized to achieve size reduction, then the device size is reduced, but sound pressure decreases especially in the low frequency range
Solution Approach 1:
The patent changes the geometric parameters of the internal electrode by chamfering the corners, which modifies the electric field distribution and stress distribution within the piezoelectric element. This parameter change allows the miniaturized device to maintain higher sound pressure output by optimizing the utilization of the piezoelectric material volume.
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 design effectively suppresses dielectric breakdown and breakage at high voltages, achieving size reduction and improved sound quality with enhanced reliability in acoustic generators and electronic apparatuses.
Implementation Method 1
a piezoelectric element having a rectangular plate shape is employed
Data Source
Figure 1(a)~1(c)
Figure 2
Figure 3
AI summary
There is provided a piezoelectric element in which dielectric breakdown or breakage is less prone to occur even in long term use at a high voltage; and an acoustic generator, an acoustic generation device, and an electronic apparatus employing the same. A piezoelectric element of the invention includes: a stacked body (13) in which a plurality of internal electrodes (11) and piezoelectric layers (12) are laminated, the stacked body having a rectangular shape in a plan view thereof; and a plurality of connecting electrodes (14) connected to one ends of the plurality of internal electrodes (11), respectively, corner portions (110) of the other ends of the plurality of internal electrodes (11) being chamfered.