Nozzle Row Thinning for Wind Ripple Suppression in Ink Jet Printers
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Solution Overview
Problem
Existing liquid droplet discharge apparatuses, such as ink jet printers, suffer from image quality issues due to turbulence caused by simultaneous discharge of ink droplets through all nozzles in the sub-scanning direction, leading to band-like density unevenness known as 'wind ripple', which results in lower image quality.
Innovation Solution
The apparatus introduces a thinned-out portion on raster lines formed by nozzles in specific regions, ensuring that not all nozzles discharge liquid droplets simultaneously in the sub-scanning direction, thereby eliminating obstacles and reducing turbulence. This is achieved by setting predetermined distances for nozzle regions and adjusting nozzle usage rates to maintain an average usage rate of 70% to 90% in the third region and below 1% at the ends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If liquid droplets are discharged through all nozzles simultaneously in the sub-scanning direction, then productivity is improved by completing image formation in fewer passes, but turbulence is generated causing wind ripple that deteriorates manufacturing precision
Solution Approach 1:
The patent segments the nozzle row into multiple regions (first region, second region, third region) along the sub-scanning direction, with each region having different nozzle usage rates. This segmentation allows simultaneous discharge of liquid droplets while creating thinned-out portions that reduce turbulence and prevent wind ripple, thus maintaining both productivity and manufacturing precision.
2Quantity of substance
If 100% printing is performed through all nozzles, then quantity of substance deposited is maximized for complete image coverage, but shade unevenness occurs due to transportation errors that deteriorates manufacturing precision
Solution Approach 1:
The patent applies different nozzle usage rates to different regions along the sub-scanning direction. The first and second regions have higher usage rates (including 100% printing) to ensure complete coverage, while the third region has reduced usage rate (thinned-out portions) to create spacing that reduces turbulence. This local differentiation maintains quantity of substance where needed while improving shade uniformity through strategic thinning.
3Area of stationary object
If nozzles at end portions discharge liquid droplets at high usage rate, then image coverage is improved at boundaries, but boundary portion quality deteriorates when transportation errors occur
Solution Approach 1:
The patent differentiates nozzle usage rates between end regions (first and second regions) and the central region (third region). The end regions maintain high usage rates including 100% printing to ensure complete image coverage at boundaries, while the central region implements thinned-out portions. This local quality differentiation optimizes both coverage and quality for their respective functional requirements.
Data Source
AI summary
The liquid droplet discharge apparatus (ink jet printer) includes a head having a nozzle row in which nozzles capable of discharging liquid droplets onto paper as a medium are aligned, and a carriage unit as a movement portion which moves the head relatively to the paper, the ink jet printer discharging the liquid droplets onto the paper through the nozzles by causing the head to perform main scanning a plurality of number of times by the carriage unit. In the ink jet printer, when a region from a nozzle at one end to a first nozzle located at a position away from the nozzle at the one end by a first predetermined distance is set to a first region, a region from a nozzle at the other end at an opposite side to the one end to a second nozzle located at a position away from the nozzle at the other end by a second predetermined distance is set to a second region, and a region between the first region and the second region is set to a third region on the nozzle row, a thinned-out portion is present on each of raster lines formed by nozzles in the third region.