Inkjet Head Nozzle Flushing Control for Image Quality
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Solution Overview
Problem
Ink jet printers face issues with image quality deterioration and reduced throughput due to nozzle clogging at connecting portions of line heads, where nozzle density is higher, and uniform flushing methods can lead to stripe-shaped unevenness and insufficient flushing.
Innovation Solution
A printing apparatus with a control unit that adjusts the liquid discharge amount per nozzle based on its location, with a larger amount discharged for nozzles not in overlap areas compared to those in overlap areas, ensuring necessary flushing and preventing clogging, while maintaining image quality and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform flushing is performed through all nozzles regardless of location, then nozzle clogging is prevented, but stripe-shaped unevenness appears in the image quality at connecting portions
Solution Approach 1:
The patent applies local quality by differentiating the flushing ink discharge amount based on nozzle location. Nozzles at connecting portions (overlap areas) discharge a smaller amount of ink during flushing compared to nozzles at non-connecting portions. This localized adjustment prevents stripe-shaped unevenness at connecting portions while maintaining adequate flushing for all nozzles, thus resolving the contradiction between preventing nozzle clogging and maintaining image quality.
2Manufacturing precision
If flushing ink discharge amount is reduced at connecting portion nozzles to prevent stripe-shaped unevenness, then image quality is maintained, but insufficient flushing occurs leading to nozzle clogging
Solution Approach 1:
The patent implements local quality by setting different flushing ink discharge amounts for nozzles at connecting portions versus non-connecting portions. Specifically, nozzles at overlap areas discharge a controlled smaller amount of ink during flushing, which prevents stripe-shaped unevenness while still providing sufficient flushing to prevent clogging. This localized differentiation resolves the contradiction between maintaining image quality and preventing nozzle clogging.
3Reliability
If heads are connected with intentional overlap to accommodate attachment errors, then assembly reliability is improved, but nozzle density increases at connecting portions causing image quality deterioration
Solution Approach 1:
The patent addresses the increased nozzle density at connecting portions by applying local quality control to the flushing operation. Nozzles located at overlap areas (connecting portions) are assigned a smaller ink discharge amount during flushing compared to nozzles at non-connecting portions. This localized adjustment compensates for the higher nozzle density and prevents stripe-shaped unevenness, thereby maintaining image quality while preserving the assembly reliability benefits of intentional overlap.
4Reliability
If flushing is performed through overlapped nozzles onto transport belt as in prior art, then nozzle clogging is prevented, but throughput of printing is lowered
Solution Approach 1:
The patent applies continuity of useful action by integrating flushing operations with the continuous printing process. Instead of performing separate flushing operations that would interrupt printing and reduce throughput, the patent performs flushing continuously during normal printing operations. By controlling the ink discharge amount based on nozzle location (smaller amount at connecting portions), the system maintains adequate flushing to prevent clogging while keeping the printing process continuous and maintaining high throughput.
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 configuration ensures uniform visibility of flushing dots across the print medium, preventing stripe-shaped unevenness and nozzle clogging, thereby maintaining image quality and preventing throughput reduction.
Implementation Method 1
a plurality of nozzles 22 which open in a nozzle opening surface 23 and through which ink is discharged
Implementation Method 2
if such a state continues that ink is not discharged through the nozzles, moisture of the ink evaporates through the openings of the nozzles so that viscosity of the ink increases
Data Source
AI summary
A printing apparatus that includes a head unit in which a plurality of heads are disposed so that parts of nozzle rows overlap with each other between the heads and a control unit configured to make the head unit execute a specified operation for forming flushing dots other than image formation dots on a print medium by discharging liquid through the nozzles. The control unit makes the head unit execute the specified operation in which a liquid amount discharged in the specified operation per nozzle that does not belong to an overlap area where parts of the nozzle rows overlap with each other between the heads is larger in a set movement distance thereof than a liquid amount discharged in the specified operation per nozzle that belongs to the overlap area in a set movement distance thereof, if a specified condition for execution of the specified operation is satisfied.