Layered Piezoelectric Pressure Sensor for Liquid Discharge Heads
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Solution Overview
Problem
Piezoelectric ceramic sensors with a single layer exhibit limited deformation under stress, leading to small permittivity changes and low detection sensitivity for pressure measurement.
Innovation Solution
A pressure detection element with a first and second piezoelectric layer in different crystal systems, where the second piezoelectric layer has a smaller thickness and lower Young's modulus than the first, enhancing capacitance change and sensitivity by increasing distortion under pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single layer piezoelectric ceramic is used, then the device complexity is reduced, but the detection sensitivity deteriorates due to small deformation and small permittivity change
Solution Approach 1:
The piezoelectric ceramic is divided into multiple layers (first piezoelectric layer and second piezoelectric layer) with different crystal systems. The first layer has rhombohedral crystal system and the second layer has tetragonal, cubic, or monoclinic crystal system. This segmentation allows each layer to contribute differently to the overall deformation, increasing the total permittivity change and detection sensitivity while maintaining a relatively simple layered structure.
Solution Approach 2:
The patent uses a composite piezoelectric structure combining materials with different crystal systems (rhombohedral and tetragonal/cubic/monoclinic). This composite approach leverages the different deformation characteristics of each crystal system to achieve larger overall deformation and permittivity change under applied stress, thereby improving detection sensitivity without significantly increasing device complexity.
2Measurement precision
If the second piezoelectric layer has smaller thickness and lower Young's modulus, then the permittivity change and capacitance variation increase, but the manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the thickness ratio between the first and second piezoelectric layers, making the second layer thinner than the first layer. It also selects materials with appropriate Young's modulus values for each layer. By carefully controlling these parameters (thickness and material properties), the patent achieves maximum permittivity change and capacitance variation while keeping manufacturing within feasible precision limits.
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 configuration allows for high sensitivity pressure detection by maximizing permittivity change and capacitance variation, enabling more accurate pressure measurement in liquid discharge applications.
Implementation Method 1
a first piezoelectric body that is disposed between the first and second electrodes and capacitance of which changes in accordance with the pressure of the pressure detection chamber
Data Source
AI summary
A pressure detection element includes a pressure detection chamber for detecting pressure inside, a first electrode, a second electrode, and a first piezoelectric body that is disposed between the first and second electrodes and capacitance of which changes in accordance with the pressure of the pressure detection chamber. The first piezoelectric body includes a first piezoelectric layer positioned on the first electrode side and a second piezoelectric layer positioned on the second electrode side. The second piezoelectric layer is in the tetragonal, cubic, or monoclinic crystal system. The first piezoelectric layer is in the rhombohedral crystal system. Thickness of the second piezoelectric layer is smaller than thickness of the first piezoelectric layer.