Piezoelectric Sensor Capacitance Increase via Dielectric Film
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Solution Overview
Problem
Piezoelectric elements with polyvinylidene fluoride films sandwiched between electrodes face issues of low capacitance, leading to high voltages that exceed detection circuit limits, vulnerability to noise, and rapid charge dissipation, which shortens detection time.
Innovation Solution
A piezoelectric element design that includes a piezoelectric film with a dielectric film in between two reference potential electrodes and a signal electrode, forming a capacitive element in parallel to increase capacitance, using polylactic acid as the piezoelectric resin and copper for the signal electrode to prevent ionization, and configuring the dielectric film to have a higher dielectric constant and thinner thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezoelectric film with piezoelectric resin is used, then the piezoelectric element can generate voltage through distortion, but the capacitance becomes low causing high voltage that exceeds detection circuit limits
Solution Approach 1:
The patent combines the piezoelectric film (with piezoelectric resin) and the dielectric film into a single integrated film structure. This merged film is disposed between the first and second reference potential electrodes, creating a combined capacitor that increases total capacitance while maintaining voltage generation capability, thus resolving the contradiction between low capacitance and high voltage output
Solution Approach 2:
The invention uses a composite film structure comprising both piezoelectric resin and dielectric material in one integrated layer. This composite material approach allows the film to simultaneously provide piezoelectric voltage generation and increased capacitance through the dielectric component, preventing voltage from exceeding detection circuit limits
2Device complexity
If a piezoelectric film with low capacitance is used, then the structure remains simple, but noise significantly influences the voltage output
Solution Approach 1:
By merging the piezoelectric and dielectric functions into a single integrated film, the patent increases capacitance without adding separate discrete capacitor components. This maintains structural simplicity while the increased capacitance naturally filters noise, reducing its influence on voltage output
3Volume of moving object
If a piezoelectric element with low capacitance is used, then the device remains compact, but the time constant becomes low causing rapid charge dissipation
Solution Approach 1:
The integrated film structure combining piezoelectric and dielectric layers increases capacitance within the same compact footprint. This merged structure extends the time constant without increasing device volume, allowing charges to be retained longer for extended detection time periods
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 enhances capacitance, prevents voltage overload, reduces noise influence, and prolongs detection time by increasing the time constant, allowing for more accurate and stable voltage detection.
Implementation Method 1
Each piezoelectric film produces charges when the piezoelectric element is distorted, for example by being stretched and contracted in a predetermined direction
Implementation Method 2
A dielectric film is layered on top of the piezoelectric film, the dielectric layer having an insulation property. The combination of the signal electrode, the dielectric film and the second reference potential electrode forming a capacitor having a second capacitance
Data Source
AI summary
A capacitor is coupled in parallel with a piezoelectric unit in a sensor. The piezoelectric unit is formed by a film which is sandwiched between a signal electrode and a reference potential electrode. A capacitor is formed by a dielectric film located between the signal electrode and a reference potential electrode. As a result, the capacitance of the sensor element is higher than it would be if the sensor only contained the piezoelectric unit.