Inkjet Head Drive Waveform for Droplet Control
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Solution Overview
Problem
Existing inkjet heads generate small droplets such as satellites and ink mists, which deteriorate print quality.
Innovation Solution
The inkjet head employs a specific drive waveform that includes an expansion portion, a first weak contraction portion, a contraction portion, and a second weak contraction portion, controlled by a drive circuit to manage the volume of the pressure chamber effectively, thereby suppressing the generation of small droplets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional drive waveform is used to eject ink droplets from the nozzle, then ink ejection is achieved, but small droplets (satellites and ink mists) are generated along with the main droplets, deteriorating print quality
Solution Approach 1:
The drive waveform is segmented into multiple distinct portions (expansion portion, first weak contraction portion, contraction portion, second weak contraction portion) instead of using a single conventional waveform. This segmentation allows precise control over the pressure chamber volume changes, enabling the main droplet to be ejected while suppressing the formation of satellite droplets and ink mists through carefully timed and sized contraction phases.
Solution Approach 2:
The invention changes multiple parameters of the drive waveform including the timing, duration, and magnitude of volume expansion and contraction. Specifically, the expansion portion increases volume to eject the main droplet, while subsequent contraction portions (with different strengths and timings) control the pressure to prevent satellite droplet formation. The hold portion maintains volume for a specific duration to stabilize the ejection process.
2Speed
If the pressure chamber volume is rapidly contracted to eject ink, then ejection speed is improved, but satellite droplets and ink mists are generated
Solution Approach 1:
The drive waveform employs periodic action through multiple expansion and contraction cycles. The expansion portion rapidly increases volume for fast ejection, followed by a hold portion that maintains the expanded state, then contraction portions that progressively reduce volume. This periodic pattern of expansion-hold-contraction allows the ink to be ejected at high speed while the controlled contraction phases suppress satellite droplet formation.
Solution Approach 2:
The hold portion serves as a preliminary action before the contraction portions. By maintaining the expanded volume for a specific duration (0.4-0.6 microseconds), the ink is allowed to stabilize and form a clean meniscus at the nozzle opening before contraction begins, preventing premature satellite droplet formation during the subsequent contraction phase.
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 solution effectively reduces the generation of small droplets, improving print quality by minimizing density unevenness and ghosting, and preventing ink mist from causing malfunctions in the printer.
Implementation Method 1
the actuator comprises a piezoelectric material
Data Source
Figure 1
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Figure 4~5C
AI summary
According to one embodiment, an inkjet head includes a pressure chamber for ink, a nozzle plate including a nozzle connected to the pressure chamber, an actuator to change a volume of the pressure chamber, and a drive circuit that drives the actuator. The drive circuit drives the actuator according to a drive waveform including an expansion waveform, a first weak contraction waveform, a contraction waveform, and a second weak contraction waveform.