Piezoelectric Liquid Ejector Droplet Timing Control
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Solution Overview
Problem
Ink-jet printers face issues with the early ejection of main droplets and the subsequent attachment of satellite droplets at distant positions due to varying viscosity and temperature, leading to unstable image quality and poor recording performance.
Innovation Solution
A liquid ejector design featuring an elongate pressure chamber with a piezoelectric actuator that includes multiple stacked piezoelectric layers and electrode layers, where the active portion is positioned closer to the nozzle, allowing synchronized pressure fluctuations to control the ejection timing and prevent early ejection of main droplets, ensuring satellite droplets follow closely behind.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the pressure chamber volume is increased to improve liquid ejection velocity, then the ejection speed increases, but the satellite droplet velocity becomes insufficient causing it to attach at distant positions
Solution Approach 1:
The pressure chamber is segmented into a liquid storing chamber and a pressure chamber separated by a liquid communicating passage. This allows independent control of liquid supply and pressure application, enabling the main droplet to be ejected at high velocity while the satellite droplet is generated and controlled separately through the restrictor, resolving the contradiction between ejection speed and position precision
Solution Approach 2:
A restrictor is introduced in the liquid communicating passage to create localized flow resistance. This local quality change allows the liquid to be supplied at controlled rates, ensuring that the satellite droplet is generated with appropriate velocity to follow the main droplet closely, thereby improving attachment position precision without sacrificing main droplet ejection speed
2Productivity
If the volume of the pressure chamber is reduced to improve recording speed, then the recording speed increases, but the liquid ejection becomes unstable due to viscosity and temperature variations
Solution Approach 1:
The liquid is pre-stored in the liquid storing chamber before ejection. This preliminary action ensures that liquid is already positioned and ready for ejection, reducing the impact of viscosity and temperature variations during the actual ejection process, thereby maintaining ejection stability while enabling faster recording speeds
Solution Approach 2:
The system dynamically adjusts liquid flow through the liquid communicating passage and restrictor based on operating conditions. This dynamic control allows the system to maintain stable ejection performance across varying viscosity and temperature conditions while preserving high recording speed through optimized chamber volumes
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 design stabilizes the ejection of main droplets and reduces the distance between main and satellite droplets, enhancing image quality by maintaining consistent droplet attachment positions even with viscosity changes, and improving the overall recording performance.
Implementation Method 1
In the piezoelectric actuator, there are provided electrodes which are independent of each other, and each of which overlaps with a central area of a corresponding one of the pressure chambers in plan view. Piezoelectric layers in the actuator are deformed relative to the pressure chambers by applying voltages to the electrodes.
Data Source
AI summary
A liquid ejector including: a nozzle; a pressure chamber communicating, at one end thereof in a specific direction, with the nozzle; a liquid-store chamber; a restrictor through which the other end of the pressure chamber in the specific direction and the liquid-store chamber communicate with each other; and an actuator having a plurality of piezoelectric layers, a pair of electrode layers, and an active portion that is constituted by a portion of one of the plurality of piezoelectric layers, which portion is interposed between the pair of electrode layers, wherein the active portion is disposed at a position corresponding to the pressure chamber so as to extend in the specific direction, and has a shorter length than the pressure chamber in the specific direction, and wherein a center of the active portion in the specific direction is shifted toward the nozzle than a center of the pressure chamber in the specific direction.