Piezoelectric Liquid Ejecting Head Imprint Stabilization
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Solution Overview
Problem
Existing piezoelectric liquid ejecting heads face challenges in achieving stable ejection performance over time due to increased costs and complexity from requiring specific reference voltages, and the imprint phenomenon which shifts the hysteresis shape of the piezoelectric body, affecting coercive electric field and ejection efficiency.
Innovation Solution
A liquid ejecting head configuration where a first electrode receives a constant reference voltage, and a second electrode receives a drive voltage that changes over time, with a piezoelectric body driven by the voltage difference. The displacement amount of the diaphragm is optimized by setting the difference between the maximum and minimum drive voltage equal for both drive voltage scenarios, with the second scenario having a closer minimum drive voltage to zero, reducing the impact of the imprint phenomenon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the voltage difference between the minimum value of the drive voltage and the reference voltage is set as the voltage at the coercive electric field to increase the ejection amount, then the ejection performance is improved, but the device complexity and cost increase due to requiring specific reference voltage circuits and wirings
Solution Approach 1:
The patent extracts the reference voltage application from the piezoelectric element structure itself, making the first electrode a common electrode that does not require a separate reference voltage circuit. By applying the reference voltage to a common electrode rather than requiring individual reference voltage applications to each piezoelectric element, the circuit complexity and wiring requirements are significantly reduced while maintaining the necessary voltage difference for achieving coercive electric field and desired ejection performance
Solution Approach 2:
The first electrode serves as a common reference voltage electrode for multiple piezoelectric elements simultaneously. This multi-functional electrode structure eliminates the need for separate reference voltage circuits for each element, reducing overall device complexity while maintaining the ability to achieve the required voltage difference for coercive electric field in each piezoelectric element
2Productivity
If the reference voltage and drive voltage are set based on the initial hysteresis shape of the piezoelectric body, then the ejection amount is increased, but the ejection performance becomes unstable over time due to the imprint phenomenon shifting the hysteresis shape
Solution Approach 1:
The patent applies a preliminary voltage (reference voltage) to the first electrode before applying the drive voltage to the second electrode. This preliminary action ensures that the piezoelectric body is in a consistent initial state (with polarization aligned) before the ejection cycle begins, compensating for the imprint phenomenon's effect on hysteresis shape shifting. By establishing this baseline polarization state in advance, the system maintains stable ejection performance over time even as the piezoelectric body undergoes repeated cycling
Solution Approach 2:
The reference voltage applied to the first electrode acts as a preliminary counter-action to the imprint phenomenon. By maintaining a constant polarization state through the reference voltage before each ejection cycle, the system pre-compensates for the hysteresis shape shifts that would otherwise occur during operation, thereby maintaining stable ejection performance despite the inherent imprint effect in piezoelectric materials
3Ease of operation
If the voltage difference between the minimum value of the drive voltage and the reference voltage is set as the voltage at the coercive electric field, then the displacement amount is increased, but the number of circuits and wirings increases causing higher cost
Solution Approach 1:
The patent merges the reference voltage function into a common first electrode that serves all piezoelectric elements, rather than requiring separate reference voltage circuits for each element. This consolidation maintains the necessary voltage difference for achieving coercive electric field and adequate displacement amount while significantly reducing the total number of circuits and wirings required in the system
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 improves ejection performance while maintaining a desired ejection amount, reduces the number of circuits and wirings needed, and minimizes the impact of the imprint phenomenon on long-term ejection stability.
Implementation Method 1
a piezoelectric body provided between the first electrode and the second electrode and driven by a voltage difference between the reference voltage and the drive voltage
Implementation Method 2
a diaphragm that vibrates in response to the driving of the piezoelectric body; and a nozzle from which a liquid is ejected by the vibration of the diaphragm
Data Source
AI summary
A liquid ejecting head may include a first electrode to which a reference voltage is applied, a second electrode to which a drive voltage is applied, a piezoelectric body provided between the first electrode and the second electrode and driven by a voltage difference between the reference voltage and the drive voltage, a diaphragm that vibrates in response to the driving of the piezoelectric body, and a nozzle from which a liquid is ejected by the vibration of the diaphragm.