Liquid Ejection Head Kogation Control via Electrode Potential
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Solution Overview
Problem
Existing liquid ejection heads face issues with kogation unevenness and heater material damage due to repeated surface layer dissolution and uneven heating frequency, leading to image defects and reduced durability.
Innovation Solution
A liquid ejection apparatus with a heating element, a first protection layer, a second protection layer acting as an electrode, and a control unit that sets a potential difference between the electrodes to manage kogation formation, reducing damage and unevenness by adjusting the potential difference during printing and non-printing cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upper protection layer is dissolved repeatedly through electrochemical reaction to remove kogation, then kogation removal effectiveness is improved, but the heater surface becomes thinner and damage is more likely to occur, reducing durability
Solution Approach 1:
The patent applies preliminary action by intentionally forming kogation on heaters with low heating frequency before it becomes problematic. During non-printing periods, the control unit identifies heaters with low heating frequency and applies a potential difference to promote kogation formation on these specific heaters. This preliminary kogation formation balances the kogation distribution across all heaters before printing operations resume, preventing the need for repeated dissolution that would damage the heater surface.
2Duration of action of stationary object
If the number of printed pages increases to improve durability, then the upper limit of printed pages increases, but the difference in heating frequency among heaters becomes more pronounced, leading to kogation unevenness
Solution Approach 1:
The patent implements feedback control by continuously monitoring the heating frequency of each heater and using this information to adjust the potential difference application strategy. The control unit identifies heaters with low heating frequency based on actual printing patterns and applies targeted potential differences to these specific heaters. This feedback mechanism ensures that kogation is evenly distributed across all heaters regardless of the number of printed pages, maintaining kogation uniformity while extending head durability.
3Reliability
If potential control is used to prevent kogation attachment during printing, then kogation prevention is improved, but ejection speed control and image quality may be affected
Solution Approach 1:
The patent applies segmentation by separating the potential control into two distinct modes: during printing, a first potential difference is applied to prevent kogation attachment and ensure consistent ejection speeds; during non-printing periods, a second potential difference is applied to intentionally form kogation on heaters with low heating frequency. This segmentation allows each mode to optimize its specific function without interfering with ejection speed consistency during printing.
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 effectively reduces kogation unevenness and extends the life of the heater material by controlling kogation formation, ensuring consistent ejection speeds and improved image quality while minimizing material damage.
Implementation Method 1
a heating resistive element heats the ink to cause bubbling
Implementation Method 2
an upper protection layer is arranged in a region including a heat applying portion of a heater, the upper protection layer arranged to be capable of being electrically connected to serve as an electrode for causing electrochemical reaction with an ink
Data Source
AI summary
An aspect of the present invention is a liquid ejection apparatus including: a liquid ejection head including a heating element, a first protection layer, a second protection layer that functions as a first electrode, a second electrode that is electrically connected to the first electrode, and an ejection port; and a control unit configured to perform control of setting a potential difference between potentials of the first and second electrodes to a predetermined value by changing at least one of the potentials of the first electrode and the second electrode, in which the control unit sets the potential difference to a first value in a case where printing is performed, and the control unit sets the potential difference to a second value different from the first value and feeds power to at least one of a plurality of the heating elements in a case where printing is not performed.