Curved Internal Electrodes in Piezoelectric Actuators
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Solution Overview
Problem
There is a growing demand for piezoelectric actuators that can produce larger flexural vibrations with lower power consumption, particularly for applications in piezoelectric vibration apparatuses and portable terminals, where existing actuators fall short in achieving efficient energy use and minimizing stress-related quality degradation.
Innovation Solution
The design incorporates a bimorph-type piezoelectric actuator with internal electrodes that are curved at their ends, allowing for enhanced bending force development and reduced stress at the boundary between active and inactive sections, facilitating larger flexural vibrations with lower power input and minimizing the occurrence of microcracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional straight internal electrode is used, then the structure is simple and easy to manufacture, but the flexural vibration amplitude is limited and power consumption is high
Solution Approach 1:
The internal electrode is designed with a curved end portion instead of a straight configuration. This curvature allows the electrode to better conform to the bending deformation of the piezoelectric layer, improving the coupling between electrical and mechanical fields. The curved shape enables more effective utilization of piezoelectric effect during flexural vibration, thereby reducing power consumption while achieving larger vibration amplitudes.
Solution Approach 2:
The invention changes the geometric parameters of the internal electrode, specifically the curvature radius and shape of the end portion. By optimizing these parameters, the electrode structure achieves better mechanical compatibility with the piezoelectric layer during bending, improving energy conversion efficiency and reducing power consumption without excessive structural complexity.
2Force
If the internal electrode end is curved to enhance bending force, then flexural vibration amplitude increases, but stress concentration at the boundary between active and inactive sections may increase
Solution Approach 1:
The curved end portion of the internal electrode is designed with a specific curvature radius that is optimized to distribute stress more evenly. The curvature allows the electrode to gradually transition from the active to inactive section, reducing abrupt stress concentration at the boundary while maintaining effective bending force generation throughout the piezoelectric layer.
Solution Approach 2:
The internal electrode has different geometric characteristics at different locations: the main body portion provides structural support and electrical connection, while the curved end portion is specifically designed to optimize stress distribution and bending force generation. This local differentiation of electrode quality allows simultaneous achievement of high bending force and reduced stress concentration.
3Productivity
If a larger flexural vibration is achieved with conventional actuators, then more power is consumed, but energy saving is desired
Solution Approach 1:
The curved end portion of the internal electrode improves the coupling efficiency between the electrical field and mechanical deformation. This enhanced coupling allows the piezoelectric actuator to generate larger flexural vibration amplitudes with the same input power, or equivalently, achieve the same vibration amplitude with reduced power consumption, thereby resolving the contradiction between productivity and energy consumption.
Solution Approach 2:
By optimizing the geometric parameters of the curved electrode (curvature radius, length of curved portion, position relative to piezoelectric layer), the invention maximizes the piezoelectric effect utilization. This parameter optimization enables larger vibration amplitudes at lower power consumption levels, directly addressing the energy saving requirement while maintaining or improving productivity.
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 enables the piezoelectric actuator to achieve larger flexural vibrations with reduced power consumption while minimizing stress and preventing quality degradation, ensuring effective energy use and prolonged actuator performance.
Implementation Method 1
a stacked body 4 composed of internal electrodes 2 and piezoelectric layers 3 which are stacked on each other
Data Source
Figure 1(a)~2
Figure 3~6
Figure 7(a)~8
AI summary
There are provided a piezoelectric actuator capable of affording even larger flexural vibration, a piezoelectric vibration apparatus, and a portable terminal. A piezoelectric actuator (1) includes a stacked body (4) composed of internal electrodes (2) and piezoelectric layers (3) which are stacked on each other; and a surface electrode (5) disposed on at least one of main surfaces of the stacked body (4) so as to be electrically connected to the internal electrodes (2). The internal electrodes (2) each includes a first electrode (21) and a second electrode (22). The stacked body (4) comprises an active section (41) in which the first electrodes (21) and the second electrodes (22) of the internal electrodes (2) are arranged so as to overlap each other in a stacking direction thereof, and an inactive section (42) which is every section of the stacked body other than the active section (41). An internal electrode (2) placed on a one-main-surface side of the internal electrodes is configured so that its end part situated near a boundary between the active section (41) and the inactive section (42) is curved toward the other main surface.