Piezoelectric Sensor Electrode Angle and Support Asymmetry
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Solution Overview
Problem
Pressing force sensors using piezoelectric sheets with a piezoelectric constant d14 face reduced detection sensitivity due to electric charge offset from electrodes, leading to decreased detection voltage.
Innovation Solution
A pressing force sensor design featuring a flat membrane-type piezoelectric element with a support structure that allows differential distortion in orthogonal directions, preventing electric charge offset and enhancing detection voltage, utilizing a piezoelectric sheet made of polylactic acid with uniaxial stretching and specific electrode configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezoelectric sheet with piezoelectric constant d14 is used to obtain detection voltage, then the detection voltage is reduced due to electric charge offset from electrodes, but the flexibility and sufficient voltage for detection are maintained
Solution Approach 1:
The support structure is designed with asymmetric features including a through-hole positioned at a specific location and a protrusion that contacts the piezoelectric sheet at an asymmetric position. This asymmetric configuration prevents uniform electric charge distribution and offset, thereby maintaining detection sensitivity while using the flexible piezoelectric sheet with d14 constant
Solution Approach 2:
The support provides localized contact points through the protrusion and through-hole structure, creating different mechanical constraints at different locations of the piezoelectric sheet. This local differentiation in support quality prevents uniform deformation and charge offset, resolving the contradiction between flexibility and detection voltage
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 design effectively maintains detection sensitivity while using piezoelectric sheets with a piezoelectric constant d14, providing reliable and accurate detection of pressing forces without voltage reduction, and is resistant to temperature influences and mechanical stress.
Implementation Method 1
a piezoelectric sheet to be a flat membrane... The piezoelectric sheet containing the polylactic acid has a piezoelectric constant d14. The flat membrane-shaped piezoelectric element using the piezoelectric sheet obtains detection voltage by utilizing piezoelectricity caused by the piezoelectric constant d14.
Data Source
AI summary
A pressing force sensor that includes a flat membrane piezoelectric element and a support. The flat membrane piezoelectric element includes a piezoelectric sheet having a piezoelectric constant. A first electrode is formed on a first main surface of the piezoelectric sheet and a second electrode is formed on a second main surface thereof. Long directions of the first electrode and the second electrode and a uniaxial stretching direction of the piezoelectric sheet form an angle of 45°. An opening portion having an elliptical section is formed on the support. The flat membrane piezoelectric element abuts the opening portion of the support. The support and the flat membrane piezoelectric element are disposed such that the opening portion is included within an area of the second electrode.