Page-Wide Inkjet Head Circulation Control for Evaporation
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Solution Overview
Problem
Inkjet printing systems face issues with uneven color and reduced landing accuracy due to changes in ink viscosity and evaporation, leading to increased ink concentration in circulation systems, which complicates the system and increases costs when using methods like those described in Japanese Patent Laid-Open No. 2005-271337.
Innovation Solution
A printing apparatus with a page-wide liquid ejection head, a cap to cover the ejection opening, and a circulator that only circulates ink during printing operations, minimizing evaporation and maintaining ink concentration by controlling the circulation flow rate and pressure within the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ink is circulated continuously through the circulation path, then fresh ink is supplied to the nozzle to maintain ejection performance, but moisture evaporates from the nozzle front end causing ink concentration to increase gradually
Solution Approach 1:
The circulation pump operates periodically rather than continuously - circulating ink during printing operations and stopping during idle periods. This periodic operation maintains nozzle performance by supplying fresh ink when needed while preventing excessive evaporation and concentration increase during non-printing times.
Solution Approach 2:
The system dynamically adjusts circulation based on operational state - the circulation pump is activated during printing and deactivated during idle periods. This dynamic control optimizes the balance between maintaining ejection performance and preventing ink concentration increase.
2Quantity of substance
If a cap covers the ejection opening to prevent evaporation, then ink concentration increase is suppressed, but the circulation system becomes more complex
Solution Approach 1:
The patent removes the cap component from the system entirely. Instead of using a cap to prevent evaporation, the solution extracts the cap function by controlling circulation timing - stopping circulation during idle periods naturally prevents evaporation without requiring a physical cap structure.
Solution Approach 2:
The circulation control system acts as an intermediary mechanism that replaces the cap's evaporation prevention function. By controlling when circulation occurs, the system achieves the same protective effect as a cap would provide, but through a simpler control-based approach rather than a physical barrier.
3Stability of the object's composition
If concentration sensors and thick ink or dilute solution are used to maintain uniform ink concentration, then ink concentration uniformity is improved, but system complexity and cost increase
Solution Approach 1:
The patent removes concentration sensors, thick ink reservoirs, and dilute solution reservoirs from the system. Instead of actively monitoring and adjusting concentration with these components, the solution extracts the need for them by preventing concentration increase through controlled circulation timing.
Solution Approach 2:
The system maintains ink concentration uniformity through self-service mechanisms - by stopping circulation during idle periods, the system naturally prevents evaporation and concentration increase without requiring external sensors or additional ink reservoirs to monitor and adjust concentration.
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 approach effectively suppresses ink concentration increases without adding complexity or cost, ensuring consistent printing quality and reducing the impact of evaporation on ink viscosity, thereby maintaining efficient ink circulation and reducing the need for concentration sensors.
Implementation Method 1
moisture normally evaporates from the front end of the nozzle
Implementation Method 2
a circulator configured to circulate the liquid so that the liquid passes through the pressure chamber
Implementation Method 3
a print element generating energy for ejecting a liquid
Data Source
AI summary
In a printing apparatus including a circulation system circulating a liquid, a volatile component included in the liquid evaporates from an ejection opening and thus characteristics of the liquid involving with concentration, viscosity and the like change. The invention provides a printing apparatus including: a page wide type liquid ejection head that includes an ejection opening ejecting a liquid, a print element generating energy for ejecting a liquid, and a pressure chamber having the print element provided therein; a cap that covers the ejection opening; and a circulator configured to circulate the liquid so that the liquid passes through the pressure chamber, wherein a circulation of the liquid is started after the cap is opened and the circulation of the liquid is stopped in a case where an image forming operation of ejecting the liquid from the ejection opening on the basis of a job is ended.