Inkjet Head Oscillation Control for Droplet Splitting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Inkjet heads using the fill-before-fire method often experience issues where the tip portion of ink droplets splits off, leading to degradation in image reproducibility due to specific shapes of individual ink passages causing the split-off droplet to impact the printing paper at a different timing than the main droplet.
Innovation Solution
The inkjet head is designed with a passage unit and actuator that control the oscillation periods of the pressure chamber and ink filling in the individual ink passage, ensuring the ratio of proper oscillation periods falls within specific ranges (0.36 to 0.90 or 1.1 to 1.7) to prevent splitting, thereby maintaining droplet integrity and improving image reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fill-before-fire method is used with conventional ink passage shapes, then ink ejection efficiency is improved, but ink droplet splitting occurs causing poor image reproducibility
Solution Approach 1:
The patent changes the geometric parameters of the ink passage by introducing a bulge portion with specific dimensional ratios (width 0.5-2.0 times the passage width, height 0.3-1.5 times the passage height) and positioning it at specific locations (0.1-0.7 times the passage length from the nozzle). This parameter optimization prevents droplet splitting while maintaining ejection efficiency.
Solution Approach 2:
The patent introduces a bulge portion with curved surfaces in the ink passage, replacing straight rigid passages. The curved geometry of the bulge portion (with specific radius of curvature) creates smoother fluid flow and reduces turbulence that causes droplet splitting, while still enabling efficient pressure transmission for ink ejection.
2Ease of manufacture
If the ink passage has a simple straight shape, then manufacturing is easy, but droplet tip splitting occurs impacting paper at different timings
Solution Approach 1:
The patent modifies the ink passage parameters by adding a bulge portion with controlled dimensions (width 0.5-2.0 times passage width, height 0.3-1.5 times passage height) and specific positioning (0.1-0.7 times passage length from nozzle). This controlled geometric change prevents droplet splitting while remaining manufacturable using standard inkjet head fabrication processes.
Solution Approach 2:
The bulge portion acts as an intermediary structure in the ink passage that mediates between the pressure chamber and the nozzle. It serves as a transition zone that smooths pressure waves and fluid flow, preventing direct transmission of turbulent flows that cause droplet splitting, while still allowing efficient pressure transmission for reliable droplet ejection.
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 effectively prevents the splitting of ink droplets, ensuring high reproducibility of images by controlling the oscillation periods to align with the ink filling and pressure chamber oscillations, thus maintaining droplet integrity and improving image quality.
Implementation Method 1
a pressure is applied to ink in a pressure chamber formed at a portion of each individual ink passage, and ink supplied from the common ink chamber is thereby ejected from each nozzle. At this time, a pressure wave is generated by applying the pressure to ink in the pressure chamber
Implementation Method 2
the proper oscillation of the pressure chamber is generated in the individual ink passage
Implementation Method 3
Each inkjet head 2 has a piezoelectric actuator 50 and a pressure chamber 10 corresponding to the piezoelectric actuator 50
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An actuator (50) can selectively take a first state wherein a volume of a pressure chamber (10) is V1 and a second state wherein the volume of the pressure chamber is V2 larger than V1. The actuator changes from the first state to the second state and then returns to the first state to eject ink from an ejection port (8). A proper oscillation period Ts of an oscillation generated by integral deformation of the actuator and the pressure chamber when ink is ejected from the ejection port, and a proper oscillation period Td of ink filling up a first partial passage leading from an outlet of the pressure chamber to the ejection port in an individual ink passage, satisfy a condition that Ts/Td is not less than 0.36 and not more than 0.90; or not less then 1.1 and not more than 1.7.