Inkjet Head Driving Method for Stable Large Droplet Formation
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Solution Overview
Problem
Existing inkjet technologies face challenges in forming stable large droplets in short driving cycles, leading to issues with satellite formation and image quality, as the speed of larger droplets increases, causing pressure wave oscillations and impact position shifts.
Innovation Solution
A method involving a specific driving signal for the inkjet head that includes a sequence of expansion and contraction pulses without pause periods, allowing two droplets to join during flight, with optimized pulse widths to suppress satellite formation and maintain low droplet speed, thereby enhancing image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the number of driving signals is increased to form larger dots, then the dot diameter increases, but the pixel cycle becomes longer
Solution Approach 1:
Multiple droplets ejected from the same nozzle are merged together during flight to form a single large dot on the media. This combining approach allows achieving large dot diameter without proportionally increasing the number of driving signals, thus reducing the pixel cycle time while maintaining the desired dot size.
2Loss of time
If larger droplets are ejected to reduce the number of signals, then the droplet speed increases, but satellite formation occurs and impact position shifts
Solution Approach 1:
The invention uses dynamic control of multiple ejection pulses with varying timing and intensity to optimize droplet formation. By dynamically adjusting the ejection parameters and merging droplets during flight, the system achieves large dot formation with controlled droplet speed, preventing satellite formation and impact position shifts while maintaining short driving cycles.
3Volume of moving object
If droplets are made to overlap on the media to form pixels, then the dot diameter increases, but the impact position becomes unstable
Solution Approach 1:
Instead of relying on overlapping droplets that land at potentially different positions, the invention merges multiple droplets during their flight through controlled timing. This ensures that the merged droplet forms a stable, predictable impact position on the media, achieving large dot diameter with high 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 approach enables efficient formation of stable large droplets in short cycles, reducing satellite occurrence and maintaining high image quality by controlling droplet speed and impact position, thus addressing the limitations of existing technologies.
Implementation Method 1
a pressure generator which deforms an actuator wall made of a piezoelectric element in accordance with a driving signal
Implementation Method 2
two droplets which are ejected consecutively from the same nozzle are made to join during flight immediately after the ejection
Implementation Method 3
a first droplet and a second droplet join during flight
Data Source
Figure 1
Figure 2(a)~3
Figure 4(a)~5
AI summary
The purpose of the present invention is to provide an inkjet head driving method and an inkjet printing apparatus that form stable large droplets efficiently with short drive cycles, limit the occurrence of satellites, and are capable of high quality image printing. A first drive signal (PA1), which is for expanding and contracting the volume of a pressure chamber to discharge at least two droplets from the same nozzle and unite same immediately after discharge to form a large droplet, comprises a first expansion pulse (Pa1) for expanding and contracting the volume of the pressure chamber, a first contraction pulse (Pa2) for contracting and expanding the volume of the pressure chamber, a second expansion pulse (Pa3) for expanding and contracting the volume of the pressure chamber, and a second contraction pulse (Pa4) for contracting and expanding the volume of the pressure chamber, in said order. A first droplet is discharged by the application of the first expansion pulse (Pa1) and the first contraction pulse (Pa2), a second droplet is discharged by application of the second expansion pulse (Pa3) and the second contraction pulse (Pa4), and the pulse width (PWA1) of the first expansion pulse (Pa1) is 0.4 AL to 2.0 AL (wherein AL is 1/2 of the acoustic resonance period of the pressure wave in the pressure chamber).