Liquid Ejection Head Electrochemical Cleaning for Accurate Replacement Timing
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Solution Overview
Problem
Existing liquid ejection heads face issues with kogation, a phenomenon where ink components adhere to heating resistance elements due to heat, leading to unstable ejection operations, and current methods for managing the material layer thickness variations result in premature replacement despite remaining cleaning capacity.
Innovation Solution
A liquid ejection head design with first and second electrodes that elute into the liquid via electrochemical reactions, allowing for measurement of wiring resistance to determine the timing for replacement by monitoring the material layer's elution and kogation removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of cleaning operations is determined based on minimum film thickness considering manufacturing variations, then the liquid ejection head can be replaced at a safe timing, but the replacement occurs prematurely even though several more cleaning processes can be performed
Solution Approach 1:
The patent implements feedback by measuring the actual film thickness of the material layer using a thickness measurement device (such as an optical sensor or interferometer). This measured thickness value is fed back to the control system, which then dynamically adjusts the replacement timing determination. Instead of relying on predetermined cleaning counts based on minimum film thickness assumptions, the system uses real-time thickness measurements to accurately determine when the material layer has reached its replacement threshold, thereby eliminating premature replacement while maintaining reliable operation.
2Manufacturing precision
If material layer thickness variations due to process variations are considered, then manufacturing robustness is improved, but the replacement timing becomes conservative and premature
Solution Approach 1:
The patent replaces the mechanical/procedural approach of counting cleaning operations with a direct measurement-based system. Instead of using a counter that increments with each cleaning cycle and compares against a predetermined threshold, the system uses a thickness measurement device to directly measure the material layer thickness and compares this actual measurement against a replacement threshold. This substitution of direct measurement for indirect counting eliminates the conservatism introduced by manufacturing variation buffers.
3Ease of operation
If the elution amount of the material layer is managed indirectly through cleaning count, then the system is simple to operate, but the detection of actual material layer status is imprecise
Solution Approach 1:
The patent introduces a thickness measurement device as an intermediary between the material layer and the control system. This intermediary directly measures the physical thickness of the material layer and transmits this information to the control system, which then determines replacement timing based on the actual measured value rather than indirect counting. This intermediary measurement mechanism maintains ease of operation (the control system still automatically determines replacement timing) while dramatically improving measurement precision (direct thickness measurement versus indirect cleaning count estimation).
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
Enables accurate detection of the optimal replacement time for the liquid ejection head, ensuring stable ejection operations by effectively managing the material layer's elution and preventing kogation buildup.
Implementation Method 1
a voltage is applied to a heating resistance element to cause film boiling in a liquid so that the liquid is ejected by the growth energy of bubbles
Implementation Method 2
the surface of an upper protective layer of a heating resistance element is configured of a material that can elute into a liquid by an electrochemical reaction, and a positive potential is applied to the material to cause the material to elute into the liquid for removing kogation
Data Source
AI summary
A technique capable of appropriately detecting a timing for replacement of a liquid ejection head is provided. The liquid ejection head includes a first electrode configured to protect an electrothermal conversion element that ejects a liquid from an ejection port and to be capable of eluting into the liquid by an electrochemical reaction with the liquid; and a second electrode installed so as to be electrically connectable to the first electrode via the liquid. A voltage is applied to cause the second electrode to generate the electrochemical reaction with the first electrode so that the first electrode is eluted into the liquid. Polarities can be reversed between the first electrode and the second electrode for applying the voltage, and wiring resistance in a circuit including a plurality of second electrodes as a part of wiring can be measured.