Piezoelectric Inkjet Head with Dynamic Rigidity Wall
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Solution Overview
Problem
Ink jet printers face challenges in achieving high-speed performance and high resolution while suppressing bubble generation in pressure chambers, which can lead to cavitation and nozzle clogging, due to increased pressure fluctuation and decreased actuator output.
Innovation Solution
A liquid ejection head design featuring a lower wall formed by a combination of a high-rigidity base plate and a low-rigidity resin plate with an air gap, allowing different vibration characteristics between pressurized and depressurized states to reduce pressure fluctuation and prevent bubble generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin layer with low elastic coefficient is formed on the pressure chamber wall to attenuate negative pressure peaks, then bubble generation is suppressed, but actuator output decreases
Solution Approach 1:
The liquid discharge head employs dynamic rigidity control where the pressure chamber wall structure (including the thin layer and supporting ribs) provides different rigidity characteristics during pressurization and depressurization phases. During pressurization, the structure maintains high rigidity for efficient actuator force transmission, while during depressurization, the thin layer allows controlled deformation to attenuate negative pressure peaks and suppress bubble generation.
Solution Approach 2:
The thin layer with low elastic coefficient is applied locally on specific portions of the pressure chamber wall rather than uniformly across the entire structure. This localized application allows the thin layer to function effectively in attenuating negative pressure where needed, while the surrounding rigid structure and supporting ribs maintain overall structural integrity and actuator efficiency.
2Productivity
If high-speed performance and high resolution are achieved, then productivity is improved, but pressure fluctuation increases causing bubble generation
Solution Approach 1:
The pressure chamber wall structure is designed with dynamic characteristics that adapt to high-speed operation. The thin layer and rib structure provide controlled compliance during rapid pressure changes, allowing the system to achieve high printing speeds and resolutions while dampening pressure fluctuations that would otherwise cause bubble generation during depressurization.
Solution Approach 2:
The thin layer with low elastic coefficient acts as a pre-configured cushioning element on the pressure chamber wall. This structure is designed in advance to absorb and attenuate negative pressure peaks before they can cause cavitation and bubble generation, enabling reliable high-speed printing without requiring post-problem corrective measures.
3Productivity
If actuator output is increased for high-speed performance, then productivity is improved, but pressure fluctuation increases causing cavitation
Solution Approach 1:
The thin layer is strategically positioned on specific areas of the pressure chamber wall where it can most effectively attenuate negative pressure fluctuations. This localized compliance allows the system to use high-power actuators for high-speed printing while the thin layer provides targeted cushioning to prevent cavitation in critical regions.
Solution Approach 2:
The thin layer structure is designed in advance to provide cushioning against pressure fluctuations before they can cause harmful cavitation effects. This proactive design allows the system to operate actuators at high output levels for improved productivity while the pre-configured thin layer structure prevents the development of damaging negative pressure peaks.
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 maintains high output while effectively suppressing bubble generation by reducing negative pressure and pressure fluctuation in the pressure chamber, ensuring reliable ink ejection and improved print quality.
Implementation Method 1
a piezoelectric actuator 40 that pressurizes the pressure chamber 28a by deforming when a voltage is applied
Implementation Method 2
a vibration layer 25 that transmits deformation of the piezoelectric actuator 40 to the pressure chamber 28a
Implementation Method 3
the lower wall has vibration characteristics different between a pressurized state in which the pressure chamber is pressurized and a depressurized state in which the pressure chamber is depressurized, so that it is deformed so as to reduce pressure fluctuation in the pressure chamber in the depressurized state
Implementation Method 4
the natural frequency of the pressure chamber is set to be equal to or lower than 1/2 of a drive frequency
Data Source
Figure 1~3
Figure 4~6
Figure 7~8
AI summary
A liquid discharge head (10) is provided with a discharge port (34) for discharging a liquid, a pressure chamber (28a) communicating with the discharge port (34), and a piezoelectric element (40) for pressurizing the pressure chamber (28a) and causing the liquid accumulated in the pressure chamber (28a) to be discharged from the discharge port (34). The liquid discharge head (10) is configured such that at least some of the walls defining the pressure chamber (28a) include a portion of which the vibration characteristic differs in a pressurized state, in which the pressure chamber is pressurized by the piezoelectric element (40), and a depressurized state, in which the pressure chamber (28a) becomes depressurized due to the liquid being discharged from the discharge port (34) and the application of pressure to the pressure chamber (28a) being stopped, the portion that has the differing vibration characteristic mitigating the fluctuation of pressure in the pressure chamber while in the depressurized state.