Piezoelectric Speaker With Divided Electrodes For Fixed-Circumference Vibration
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Solution Overview
Problem
Conventional piezoelectric speakers mounted on display screens, such as cellular phones, compromise visual quality, are prone to dust and smudge issues due to open sides, and reduce waterproofing, while requiring specific fixation designs to vibrate effectively.
Innovation Solution
A piezoelectric speaker with a laminated body of polymer sheets, including a chiral polymer like poly-L-lactic acid, featuring divided electrodes on the vibration region to direct electric field vectors oppositely between adjacent sheet portions, allowing vibration even when the circumference is fixed, and enhancing transparency and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a transparent piezoelectric speaker is mounted on a display screen as being bent, then sound output from a wide range is enhanced, but visual quality of the device deteriorates and visibility of the display screen is reduced due to reflections
Solution Approach 1:
Instead of bending the transparent speaker as in conventional designs, this invention makes the speaker substantially planar with the display screen surface. The piezoelectric element is configured to vibrate in a direction substantially perpendicular to the display screen, allowing sound output without compromising visual quality or causing reflections that would obscure the display.
2Ease of operation
If the side face of the vibration plate is greatly open, then dusts or other smudges are easy to enter, but removing them becomes troublesome operation
Solution Approach 1:
A protective plate is provided that covers the side face of the vibration plate. This protective plate is configured to be removable, allowing easy access for cleaning when needed, while normally protecting the vibration plate from dust and smudge accumulation. The protective plate acts as a flexible barrier that can be removed for maintenance and reattached for protection.
3Stability of the object's composition
If the bimorph is fixed on four sides, then structural stability is improved, but vibration capability is significantly reduced
Solution Approach 1:
The piezoelectric element is configured with localized vibration regions that allow effective vibration even when the overall structure is fixed on four sides. The vibration is concentrated in specific areas of the piezoelectric element, enabling sound production while maintaining structural stability through the fixed edges. This localizes the vibration action to where it is most effective while keeping the boundaries fixed.
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 enables effective vibration and sound production with increased design flexibility, improved transparency, reduced power consumption, and enhanced durability, while preventing dust and smudge issues and maintaining waterproofing.
Implementation Method 1
a piezoelectric sheet made of a polymer, which exhibits piezoelectricity when it is stretched
Implementation Method 2
voltage is applied by each of the plurality of electrode portions in such a manner that electric field vectors generated in the thickness direction of the piezoelectric sheet direct in opposite directions between the adjacent ones of a plurality of sheet portions
Data Source
Figure 1~2
Figure 3~4
Figure 5(a)~6
AI summary
When a piezoelectric speaker, which has a bimorph structure, for example, and is configured by using a piezoelectric sheet having a predetermined stretching axis and made of a chiral polymer, is fixed on a whole circumference, an appropriate vibration is hindered, so that it cannot function as a speaker. An electrode (17) formed on opposing main surfaces of a piezoelectric sheet (12, 13) having a predetermined stretching axis and made of a chiral polymer is divided into four electrode portions (E1 to E4) by a plurality of dividing lines (21a, 21b, 22a, 22b) extending in a radiation direction. The four electrode portions (E1 to E4) are distributed along the outer peripheral portion except for the central portion of a vibration region 15. Voltage is applied to the respective four electrode portions (E1 to E4) in such a manner that electric field vectors generated in the thickness direction of the piezoelectric sheet (12, 13) direct in opposite directions between the adjacent ones of four sheet portions of the piezoelectric sheet (12, 13) to which voltage is applied by the electrode portions (E1 to E4).