Liquid Ejection Electrode Layout to Suppress Heat Element Kogation
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Solution Overview
Problem
Existing liquid ejection devices suffer from kogation, leading to ununiform heat conduction and unstable foaming, which reduces the durability of the device.
Innovation Solution
A liquid ejection device with a first electrode and a second electrode positioned differently from the first electrode, applying a voltage across them to generate an electric field that repels charged particles, thereby suppressing kogation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is disposed on the heat element to protect from physical and chemical effects, then the heat element is protected from damage, but kogation occurs on the protective layer surface leading to ununiform heat conduction and unstable foaming
Solution Approach 1:
The patent replaces the mechanical/physical protective layer with an electrical field-based solution. By applying a voltage between the heat element and a counter electrode, an electric field is generated that repels charged particles (kogation) before they can adsorb onto the heat element surface, eliminating the need for a protective layer and preventing ununiform heat conduction.
Solution Approach 2:
The patent introduces an intermediary substance - the electric field - between the heat element and the liquid to be ejected. This electric field acts as a mediator that prevents charged particles from directly contacting the heat element surface, thereby preventing kogation while maintaining effective heat transfer.
2Reliability
If voltage is applied to suppress kogation by repelling charged particles, then kogation is suppressed and durability is improved, but additional components (electrodes, voltage application mechanism) are required
Solution Approach 1:
The patent makes the heat element serve multiple functions: it remains the thermal processing element while also serving as one electrode in the voltage application system. This multi-functionality reduces the need for separate components and simplifies the overall device structure while achieving kogation suppression.
Solution Approach 2:
The patent merges the heat element and the first electrode into a single component. The heat element is simultaneously used for thermal processing and as an electrode for voltage application, combining two functions into one element and reducing device complexity.
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
The solution effectively suppresses kogation, improving the durability of the liquid ejection device by maintaining consistent ejection velocity and reducing particle accumulation on the heat element.
Implementation Method 1
the liquid is foamed in the liquid chamber by the film boiling thereof caused by the heating
Implementation Method 2
the liquid inside a liquid chamber is heated by electrifying a heat element
Implementation Method 3
applying a voltage across the two electrodes to generate an electric field in the liquid inside the liquid chamber
Implementation Method 4
leading to the repulsion of the charged particles in the liquid to suppress kogation
Implementation Method 5
physical effects such as the impact due to the cavitation caused when a liquid foams, contracts, and is defoamed
Implementation Method 6
the liquid is foamed in the liquid chamber by the film boiling thereof caused by the heating, and droplets are ejected from an ejection port by the foam energy
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A liquid ejection device(3) has an element substrate (10) having an ejection port (13); and a voltage application unit (900) applying a voltage to the element substrate, wherein the element substrate has a first layer (12) having the ejection port and a first channel (23) communicating with the ejection port and a second layer (11) fixed to a back face of the first layer and having a second channel (17a) communicating with the first channel, a heat element (126) for ejecting the liquid, a first electrode (133) covering a surface of the heat element on a side of the first layer and exposed to the first channel, and a second electrode (129) exposed to the first channel at a position different from the first electrode and not overlapping the heat element on a plan view, and the voltage application unit is configured to apply the voltage so that the first electrode is at a negative potential.