Inkjet Head Nozzle Usage Ratio Control for Density Uniformity
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Solution Overview
Problem
Ink jet printers face challenges in creating high-quality images due to prominent density nonuniformity caused by varying ink droplet volumes from nozzles, leading to low-quality images with different sized dots and lateral streaks during multi-pass printing.
Innovation Solution
The image forming apparatus employs a head with nozzles arranged in the sub-scanning direction, where the head moves in the main-scanning direction and the medium is transported in the sub-scanning direction, with specific nozzle usage ratios and region configurations to minimize density nonuniformity by gradually changing nozzle usage ratios between regions, and sets nozzles at the ends to have a usage ratio of 1% or less to reduce lateral streaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If different numbers of ink droplets are ejected from nozzles to create different sized dots in multi-pass printing, then the head can cover the entire medium width, but the volume of ink droplets varies causing prominent density nonuniformity and low image quality
Solution Approach 1:
The patent applies local quality by dividing the head into multiple regions (first region, second region, third region) with different nozzle configurations. The first and second regions have nozzles that eject ink droplets, while the third region has nozzles that do not eject ink droplets. This spatial differentiation of nozzle functionality allows the system to maintain consistent ink droplet volumes across different regions while still achieving complete coverage through strategic nozzle placement and regional variation in usage ratios.
Solution Approach 2:
The patent segments the head into distinct functional regions along the sub-scanning direction. The first region contains nozzles with higher usage ratios, the second region contains nozzles with lower usage ratios, and the third region contains nozzles with zero usage ratios. This segmentation allows independent optimization of each region's contribution to overall image quality while maintaining system productivity.
2Quantity of substance
If nozzles at the ends of the head are used with high usage ratios, then more ink can be deposited, but lateral streaks are generated during transport operations
Solution Approach 1:
The patent applies local quality by creating spatial variation in nozzle usage ratios across different regions. The first and second regions have nozzles with higher usage ratios for effective ink deposition, while the third region has nozzles with zero usage ratios specifically positioned to prevent lateral streaks. This localized differentiation of nozzle functionality directly addresses the contradiction between ink deposition quantity and lateral streak prevention.
Solution Approach 2:
The patent converts the potential harm of end nozzles causing lateral streaks into a benefit by strategically positioning the third region's nozzles with zero usage ratios. These nozzles would normally be problematic, but by setting their usage ratio to zero, the system turns this potential defect into a feature that prevents lateral streaks while maintaining adequate ink deposition through the first and second regions.
Data Source
AI summary
An image forming apparatus includes a head; a scanning section; and a transport section. A first region is formed in the head between a nozzle formed at a first end and a first nozzle that is a first predetermined distance away, in the sub-scanning direction, from the nozzle formed at the first end. A second region is formed in the head between a nozzle formed at a second end and a second nozzle that is a second predetermined distance away, in the sub-scanning direction, from the nozzle formed at the second end. When the head, the scanning section, and the transport section form an image on the medium, a moving-average nozzle usage ratio within a region between the first region and the second region changes at a lower rate than moving-average nozzle usage ratios within the first region and the second region.