Inkjet Density Control via Voltage and Droplet Adjustment

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Solution Overview

Problem

Inkjet image forming apparatuses face challenges in adjusting density evenly among ink heads, leading to density differences and potential colorless portions due to insufficient adjustments at low and high density levels, and inadequate optimization for ink heads with varying characteristics.

Innovation Solution

An inkjet image forming apparatus with a drive voltage controller, halftone processing controller, and density adjustment controller that adjusts ink droplet amounts and voltages across multiple ink heads to reduce density differences by printing a density adjustment pattern and calculating adjustment values for each density level, ensuring balanced ink distribution without generating colorless portions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If density adjustment is done by focusing on the intermediary density level when the scanned print pattern includes three density levels, then balance of whole density is improved, but density adjustment for the low and high density levels becomes insufficient

Engineering Contradiction:

Improvebalance of whole densityVSAvoiddensity adjustment precision for low and high density levels

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent divides the density adjustment process into three separate adjustment processes corresponding to low, intermediary, and high density levels. Each process independently adjusts the drive voltage for its specific density level, ensuring that all density levels receive adequate adjustment attention rather than focusing solely on the intermediary level.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different adjustment strategies to different density levels. For low density levels, it adjusts drive voltage to prevent colorless portions. For high density levels, it optimizes for maximum density while considering ink heads with low density characteristics. This localized adjustment approach ensures each density level receives appropriate treatment.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If density adjustment is made by halftone processing to increase or decrease the number of ink droplets, then density adjustment capability is improved, but colorless portions are generated due to increase or decrease of ink droplets

Engineering Contradiction:

Improvedensity adjustment capabilityVSAvoidcolorless portions

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent changes the adjustment parameter from the number of ink droplets (halftone processing) to drive voltage adjustment. By adjusting the drive voltage, the ink droplet amount is controlled continuously without reducing the number of droplets to zero, thereby preventing colorless portions while maintaining density adjustment capability.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If the number of ink droplets is decreased for dots with maximum density level, then density optimization for ink heads with low density characteristics is improved, but maximum density of printed dot matrix becomes insufficient

Engineering Contradiction:

Improveoptimization for ink heads with low density characteristicsVSAvoidmaximum density of printed dot matrix

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent dynamically adjusts the drive voltage based on the specific density characteristics of each ink head. For ink heads with low density characteristics, it applies higher drive voltages to compensate and achieve adequate density, while for other ink heads, it adjusts accordingly. This dynamic adjustment ensures both adaptability to different ink head characteristics and maintenance of maximum density requirements.

Inventive Principle:

Principle #15Dynamics

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 solution allows for effective density adjustment across all density levels, reducing differences among ink heads and preventing colorless portions, while maintaining adequate ink injection ranges, thereby enhancing printing quality.

Implementation Method 1

adjust density among the plurality of ink heads by controlling each drive voltage of the plurality of ink heads to change amounts of ink droplets injected from nozzles

Methodology Applied

Scientific EffectElectrostatic fluid acceleration: Electrostatic Fluid Accelerator

Data Source

PatentUS9056486B1Inkjet image forming apparatus

Publication Date: 2015.06.16 RISO KAGAKU CORP

AI summary

An inkjet image forming apparatus includes ink heads, a drive voltage controller that adjusts density by controlling each drive voltage of the ink heads, a halftone processing controller that adjusts density by changing the number of ink droplets ejected from each nozzle of the ink heads, and a density adjustment controller that prints and scans a density adjustment pattern to calculate an adjustment value of each density level. The density adjustment controller adjusts density of a lowest density level so that the drive voltage controller controls each drive voltage based on the adjustment value of the lowest density level, and adjusts density of each density level other than the lowest density level so that the halftone processing controller changes the number of ink droplets based on the adjustment value of each density level other than the lowest density level and the adjustment result by the drive voltage controller.