Piezoelectric Speaker Temperature Correction via Copolymer and Control
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Solution Overview
Problem
Piezoelectric speakers and touch input systems using flexible polymer materials face issues with sound volume and frequency fluctuations due to temperature changes, leading to poor acoustic characteristics and sensing performance, especially in high-temperature environments like bathrooms and kitchens.
Innovation Solution
A piezoelectric device with a piezoelectric element having electrodes on both surfaces, an inputting unit, a storing unit for temperature dependency data, a temperature detecting unit, and a correcting unit that adjusts input information based on detected temperature and stored data to maintain consistent performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a flexible piezoelectric polymer material such as PVDF is used for the piezoelectric film, then the device can be low in profile and light in weight, but acoustic characteristics such as sound pressure level and frequency characteristics decrease depending on ambient temperature
Solution Approach 1:
The patent applies parameter changes by modifying the piezoelectric material composition - specifically using a copolymer of vinylidene fluoride and trifluoroethylene with a specific compositional ratio (70:30 to 80:20). This compositional parameter change results in a material with improved temperature stability while maintaining flexibility and piezoelectric properties, thereby resolving the contradiction between low profile/light weight and acoustic characteristics stability across temperature variations
Solution Approach 2:
The patent employs composite materials by creating a copolymer structure combining vinylidene fluoride and trifluoroethylene monomers. This composite polymer structure leverages the complementary properties of both monomer types to achieve enhanced temperature resistance while preserving the flexibility and piezoelectric effect needed for thin-film speaker applications, thus maintaining acoustic performance stability across different ambient temperatures
2Ease of operation
If the piezoelectric constant fluctuates due to temperature change, then the sound volume fluctuates, but using conventional piezoelectric materials results in poor touch pressure resolution and vulnerability to external impact
Solution Approach 1:
The patent modifies material parameters by selecting a specific copolymer composition (vinylidene fluoride-trifluoroethylene in 70:30 to 80:20 ratio) that inherently provides both improved mechanical strength and reduced temperature dependency of the piezoelectric constant. This parameter optimization enables the material to maintain stable piezoelectric properties across temperature ranges while possessing sufficient mechanical robustness to resist external impacts better than conventional PVDF materials
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 solution ensures stable sound volume and quality in piezoelectric speakers and accurate sensing performance in touch input systems, even under varying environmental temperatures, by correcting for temperature-induced changes in piezoelectric constant and Young's modulus.
Implementation Method 1
a piezoelectric film speaker which includes a piezoelectric film diaphragm formed by transparent electrodes on front and back surfaces of a transparent and flexible piezoelectric film
Implementation Method 2
a touch input system using a piezoelectric polymer material as an element material
Data Source
AI summary
A piezoelectric device is provided with a sound source IC, an amplifier for amplifying a sound source from the sound source IC, a piezoelectric speaker for generating sound based on a drive signal from amplifier, an MPU for performing a predetermined control process on the drive signal, a memory for storing temperature dependency information about the piezoelectric constant (d14) and Young's modulus E of the piezoelectric speaker, and a temperature sensor for detecting an ambient temperature. MPU has correcting unit, compares a detected result of the temperature sensor with the temperature dependency information, and performs temperature correction on the drive signal serving as an acoustic signal based on a compared result. The piezoelectric speaker outputs the acoustic signal temperature-corrected by correcting unit. Thus, it becomes possible to realize various piezoelectric devices, such as a piezoelectric speaker system, capable of preventing various input information from fluctuating even when there is a change in usage environmental temperature.