Liquid Ejection Head Bubble Discharge for Stable Ink Pressure
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Solution Overview
Problem
Existing liquid ejection systems face issues with ejection failure and ink leakage due to trapped bubbles in the permeable defining walls, which can expand and cause pressure imbalances, especially when left unused or under varying environmental conditions.
Innovation Solution
A liquid ejection head and apparatus design that includes a circulation unit with a unidirectional pump and on-off valves to manage pressure and bubble discharge, using a flexible intermediate tank and pressure chambers to maintain stable ink supply and discharge bubbles effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a permeable defining wall with certain thickness is used to trap and permeate bubbles, then bubble collection is achieved, but permeation time increases and ejection failure may occur
Solution Approach 1:
The patent introduces a bubble discharge unit with a depressurization chamber that actively removes bubbles before they can expand and cause problems. By performing preliminary bubble discharge through the permeable defining wall into the depressurization chamber, the system prevents the time delay and ejection failures that would otherwise occur during normal operation.
Solution Approach 2:
The patent extracts bubbles from the ink supply system by providing a dedicated bubble discharge unit separate from the main ink circulation path. The permeable defining wall allows bubbles to be removed from the ink and collected in the depressurization chamber, where they are then discharged through the gas discharge port, preventing them from causing ejection failures.
2Reliability
If bubbles are trapped in the upstream channel, then gas collection is achieved, but bubbles may expand under environmental changes and cause ink leakage
Solution Approach 1:
The patent converts the harmful effect of trapped bubbles into a beneficial discharge mechanism. The permeable defining wall, which initially seemed to merely collect bubbles, is designed to actively discharge them into the depressurization chamber. The bubbles that would otherwise expand and cause ink leakage are instead routed through a controlled path to the gas discharge port, where they are safely expelled.
Solution Approach 2:
The depressurization chamber acts as an intermediary between the ink supply channel and the external environment. Bubbles are transferred from the ink supply through the permeable defining wall into this intermediate chamber, which then provides a safe pathway for bubble discharge without allowing them to expand into the ink or cause leakage.
3Reliability
If a circulation unit with pump and valves is added to manage pressure and bubbles, then ejection stability is improved, but device complexity increases
Solution Approach 1:
The circulation unit is designed to perform multiple functions: it circulates ink, manages pressure, and facilitates bubble discharge through the same integrated system. The pump, check valves, and permeable defining wall work together to achieve both ink circulation and bubble removal, reducing the need for separate dedicated components for each function.
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 design suppresses ejection failure and ink leakage by maintaining stable pressure and efficiently managing bubbles, ensuring consistent ink ejection performance.
Implementation Method 1
a unidirectional pump 404 configured to circulate the ink
Implementation Method 2
the gas in the trapped bubbles permeates through the permeable defining wall
Implementation Method 3
a flexible intermediate tank 402 disposed between the ink tank 2 and the liquid ejection head 1
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An object is to provide a liquid ejection head (1) and liquid ejection apparatus (50) capable of suppressing the occurrence of ejection failure and ink leakage. To this end, the amount of gas permeation through a region of a gas permeable membrane (710) of polypropylene (PP) with an area of 0.36 cm2 is set to 0.01 cc/day or more in a case where the pressure difference between a bubble accumulation chamber (520) and a depressurization chamber (760) is set to 50 kPa.