Piezoelectric Pump Neutral Plane Alignment
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Solution Overview
Problem
Piezoelectric pumps with bimorph structures face inefficiencies due to neutral plane deviation, leading to reduced displacement and increased heat generation, as the piezoelectric element portions move against bending, hindering pump performance.
Innovation Solution
Incorporating a neutral layer within the bimorph piezoelectric element that does not displace when a voltage is applied, positioning the neutral plane within this layer to prevent opposing stresses, allowing all piezoelectric element portions to bend uniformly, thereby enhancing displacement and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a bimorph piezoelectric element is used to drive the diaphragm unit, then the pump can operate at relatively low frequencies with good efficiency, but the neutral plane deviates from the diaphragm causing portions of the piezoelectric element to move against bending, decreasing displacement and pump efficiency while increasing heat generation
Solution Approach 1:
The piezoelectric element is segmented into multiple layers with different polarization directions. The upper piezoelectric layer is polarized in one direction while the lower piezoelectric layer is polarized in the opposite direction, allowing each layer to contribute constructively to the bending motion without internal stress conflict
Solution Approach 2:
The bimorph structure uses asymmetric polarization configuration where the upper and lower piezoelectric layers have opposite polarization directions. This asymmetric design allows the neutral plane to be positioned optimally within the piezoelectric element, preventing portions from moving against bending and reducing energy loss
2Loss of energy
If the neutral plane is not positioned in the diaphragm, then portions of the piezoelectric element move against bending, but repositioning the neutral plane requires adjusting thicknesses which complicates manufacturing
Solution Approach 1:
The invention changes the polarization direction parameter of the piezoelectric layers rather than adjusting thickness parameters. By reversing the polarization direction of the lower layer while maintaining standard thickness ratios, the neutral plane is repositioned to the center of the piezoelectric element without complex manufacturing adjustments
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 stabilizes the neutral plane, preventing unwanted stress and heat generation, resulting in improved displacement and pump efficiency by ensuring all piezoelectric elements bend in sync, thus enhancing the overall performance of the piezoelectric pump.
Implementation Method 1
Piezoelectric micro pumps utilize diaphragms that bend when a voltage is applied to piezoelectric elements
Data Source
Figure 1~3
Figure 4~6(b)
Figure 7~8
AI summary
[Object] In a diaphragm-type piezoelectric pump using a bimorph piezoelectric element, a factor that hinders the displacement of the piezoelectric element is removed so as to provide an efficient piezoelectric pump. [Solving Means] A piezoelectric pump includes a diaphragm 21 that forms a pump chamber 12 between the diaphragm and a pump body 10, and a piezoelectric element 22 bonded face-to-face to a surface of the diaphragm. The piezoelectric element 22 is a bimorph piezoelectric element in which a plurality of piezoelectric layers are stacked, including a neutral layer 22b that does not spontaneously become displaced in the middle of the piezoelectric element in the thickness direction. The piezoelectric element 22 can efficiently become displaced, because a neutral plane Fd of the entire diaphragm combined with the piezoelectric element is positioned in the neutral layer 22b.