Piezoelectric Drive Element Composite Ceramic Resonance Stability
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Solution Overview
Problem
Resonant actuators using bismuth layered compounds exhibit low piezoelectric characteristics, leading to reduced mechanical quality coefficients and instability when driven at resonance frequencies, especially when the AC electric field is increased to enhance vibration speed.
Innovation Solution
A composite ceramic is created by combining a first piezoelectric ceramic with soft spring characteristics and a second piezoelectric ceramic with hard spring characteristics, where external electrodes are applied to maintain stability at resonance frequencies by adjusting the elastic constant in response to increased vibration speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the AC electric field is increased to enhance vibration speed, then the vibration speed is improved, but the resonance frequency fluctuates and the actuator becomes unstable
Solution Approach 1:
The patent changes the physical-chemical parameters of the piezoelectric material by developing a composite ceramic system with specific composition ratios (first piezoelectric ceramic: second piezoelectric ceramic = 1:4 to 4:1). This parameter change in material composition enables the elastic constant to increase with vibration speed, thereby stabilizing resonance frequency while allowing high vibration speeds.
Solution Approach 2:
The patent uses composite materials by combining two different piezoelectric ceramics with distinct characteristics. The first piezoelectric ceramic provides piezoelectric effect, while the second piezoelectric ceramic contributes to increasing elastic constant with vibration speed. This composite structure resolves the contradiction between achieving high vibration speed and maintaining resonance frequency stability.
2Speed
If conventional PZT piezoelectric ceramics are driven at resonance frequency to increase vibration speed, then the vibration speed is improved, but the resonance frequency and mechanical quality coefficient drop
Solution Approach 1:
The patent fundamentally changes the material parameters by replacing conventional PZT ceramics with a composite system where the second piezoelectric ceramic component causes the elastic constant to increase with vibration speed. This parameter change prevents the resonance frequency and mechanical quality coefficient from dropping, allowing stable operation at high vibration speeds.
Solution Approach 2:
The patent employs composite piezoelectric ceramic materials combining two different ceramic systems. This composite approach leverages the complementary characteristics of both materials to achieve both high vibration speed and stable resonance frequency, overcoming the limitations of single-material PZT actuators.
3Stability of the object's composition
If bismuth layered compounds are used to achieve high vibration levels, then the mechanical quality coefficient is improved, but the piezoelectric characteristics are reduced
Solution Approach 1:
The patent applies local quality by assigning different functional roles to different components within the composite ceramic. The first piezoelectric ceramic locally provides piezoelectric characteristics, while the second piezoelectric ceramic locally contributes to mechanical quality and elastic constant behavior. This spatial-functional differentiation resolves the contradiction between piezoelectric characteristics and mechanical quality.
Solution Approach 2:
The patent uses composite materials to combine the advantages of different piezoelectric ceramic systems. By integrating two different piezoelectric ceramics in specific ratios, the composite material simultaneously achieves good piezoelectric characteristics and high mechanical quality coefficient, overcoming the trade-off present in single-material systems.
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 composite ceramic suppresses resonance frequency fluctuation, allowing the piezoelectric drive element to be driven stably at and near resonance frequencies even when the AC electric field is raised, by adjusting the elastic constant to maintain consistent vibration speed.
Implementation Method 1
an AC electric field is applied to the external electrodes to drive the piezoelectric drive element
Data Source
AI summary
A piezoelectrically actuated element includes a composite ceramic to which an alternating electric field is applied through external electrodes that are orthogonal to the polarization direction, wherein the composite ceramic is formed from a first piezoelectric ceramic having soft spring characteristics such that the elastic constant decreases with increasing vibration velocity, and a second piezoelectric ceramic having hard spring characteristics such that the elastic constant increases with increasing vibration velocity. Even when the applied electric field is intensified to increase the vibration velocity of the piezoelectrically actuated element, the overall change in the elastic constant is minimized, and fluctuations in the resonance frequency is suppressed.