Piezoelectric Element Thickness Asymmetry in Droplet Ejection Head
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Piezoelectric elements with low piezoelectric constants, such as those using potassium sodium niobate (KNN), experience overshoot and abnormal droplet ejection due to insufficient displacement of the vibration plate, especially when subjected to high-frequency driving pulses, leading to unintended displacement and ejection issues.
Innovation Solution
A droplet ejection head design featuring a piezoelectric element with a KNN layer, where the total thickness of the piezoelectric layer, first electrode, and second electrode is greater than the vibration plate thickness, ensuring a displacement twice that of the vibration plate when a voltage is applied, and incorporating asymmetry in the piezoelectric element's displacement response to voltage direction to reduce overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the thickness of the vibration plate is reduced to increase displacement amount, then the displacement amount of the vibration plate is increased, but unintended displacement of the vibration plate occurs as overshoot
Solution Approach 1:
The patent applies asymmetry by making the piezoelectric layer thickness asymmetric relative to the vibration plate thickness. Specifically, the piezoelectric layer thickness is designed to be greater than the vibration plate thickness, creating an asymmetric structure that generates sufficient driving force while maintaining stability. This asymmetric configuration ensures that the piezoelectric element can produce adequate displacement without causing overshoot, thereby resolving the contradiction between increasing displacement and preventing abnormal ejection.
Solution Approach 2:
The patent employs parameter changes by optimizing the thickness parameters of both the vibration plate and piezoelectric layer. By carefully controlling the piezoelectric layer thickness to be greater than the vibration plate thickness, the system achieves the desired displacement amount while preventing overshoot. This parameter optimization allows the vibration plate to respond adequately to driving signals without unintended displacement, thus resolving the contradiction between displacement amount and ejection stability.
2Speed
If a high frequency driving pulse is supplied to the piezoelectric element, then the ejection speed is improved, but bending deformation of the vibration plate cannot follow switching and an overshoot occurs
Solution Approach 1:
The asymmetric structure where the piezoelectric layer thickness exceeds the vibration plate thickness enables the system to respond effectively to high-frequency driving pulses. This configuration provides sufficient driving force to follow rapid voltage transitions while maintaining stability, preventing overshoot even at high frequencies. The asymmetry ensures that the vibration plate can keep up with the driving waveform switching without bending deformation issues.
Solution Approach 2:
The patent applies dynamics by optimizing the mass and stiffness characteristics of the vibration plate through thickness control. By making the piezoelectric layer thicker than the vibration plate, the system achieves appropriate dynamic response to high-frequency signals. This dynamic configuration allows the vibration plate to follow the driving waveform transitions accurately without overshoot, enabling high-speed ejection while maintaining reliability.
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 the responsiveness of the vibration plate to driving voltage, reducing high-frequency vibrations and preventing abnormal ejections by maintaining stable displacement during droplet ejection, thereby improving the reliability of the droplet ejection process.
Implementation Method 1
a piezoelectric element containing potassium, sodium, and niobium and formed on the vibration plate
Data Source
AI summary
A droplet ejection head includes a nozzle plate having a nozzle, a pressure chamber forming substrate having a pressure chamber, a vibration plate, and a piezoelectric element containing potassium, sodium, and niobium and formed on the vibration plate. The piezoelectric element includes a first electrode, a second electrode, and a piezoelectric layer located between the first electrode and the second electrode. A total thickness of the piezoelectric layer, the first electrode, and the second electrode is larger than a thickness of the vibration plate. An absolute value of a displacement amount of the vibration plate when a voltage having an absolute value of 25 V is applied to the piezoelectric element as a voltage for displacing the vibration plate in a direction in which a volume of the pressure chamber expands is twice or more an absolute value of a displacement amount of the vibration plate when a voltage having an absolute value of 25 V is applied to the piezoelectric element as a voltage for displacing the vibration plate in a direction in which a volume of the pressure chamber contracts.