Inkjet Sub-Tank Air-Discharge Valve Control
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Solution Overview
Problem
Ink-ejection instability in liquid-ejection apparatuses due to prolonged exposure of ink to ambient air, causing viscosity increases and unstable ejection.
Innovation Solution
A liquid-ejection apparatus with a sub-tank system that includes a controller to temporarily open and close an air-discharge valve, preventing prolonged exposure of ink to ambient air by controlling air discharge operations, ensuring the ink remains in an airtight state during non-operational periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the air-discharge valve is kept opened to resolve pressure difference between sub-tank and head, then the pressure balance is improved, but the ink is exposed to ambient air for long time causing viscosity rise and unstable ejection
Solution Approach 1:
The air-discharge valve is opened in advance during ink filling operation to allow air bubbles to escape from the ink channel before ejection begins. The valve is then closed before ejection starts, preventing ink exposure to ambient air during the critical ejection phase while maintaining pressure balance during filling.
Solution Approach 2:
The air-discharge valve transitions from a static open state in conventional designs to a dynamic controlled state in this invention. The controller opens the valve during ink filling when air discharge is needed, closes it during ejection to maintain ink stability, and opens it again during air discharge operations. This dynamic control resolves the contradiction between pressure balance and ink stability.
2Object-generated harmful factors
If the air-discharge valve is opened to discharge air bubbles from sub-tank, then air discharge function is improved, but ink viscosity rises due to prolonged ambient air exposure
Solution Approach 1:
Air bubbles are discharged during the ink filling operation before ejection begins. The valve is opened at this preliminary stage to remove air bubbles from the system, then closed before ejection to prevent ink exposure. This timing separates the air discharge function from the ejection function, resolving the contradiction.
Solution Approach 2:
The ink filling, air discharge, and ejection operations are sequenced continuously with proper valve control. Ink fills while valve is open for air discharge, then valve closes and ejection begins without interruption. This continuous operation ensures air bubbles are removed before they can interfere with ejection, while ink stability is maintained during the critical ejection phase.
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 stabilizes ink ejection by maintaining ink viscosity and preventing air bubbles, thus ensuring consistent and reliable ink flow, reducing wear on pumps and minimizing unnecessary ink consumption.
Implementation Method 1
a liquid-supply pump configured to supply the liquid in the main tank to the head
Implementation Method 2
When an ink with which air bubbles are mixed is supplied from the head into the sub-tank, the air bubbles are moved upward in the sub-tank to be discharged from the upper portion thereof to the ambient air
Data Source
AI summary
A liquid-ejection apparatus, including: a head configured to eject a liquid from a plurality of liquid-ejection openings; a main tank configured to accommodate the liquid supplied to the head; a liquid-supply pump configured to supply the liquid in the main tank to the head; a sub-tank in which are formed (a) a connection opening for connecting the sub-tank to the head and (b) an air-discharge opening for communicating the sub-tank with ambient air; a first channel extending from the liquid-supply pump to the sub-tank via the head and the connection opening; a second channel extending from the sub-tank to the liquid-supply pump; a third channel extending from the air-discharge opening of the sub-tank to the ambient air; an air-discharge valve provided in the third channel so as to be openable and closable; and a controller configured to control the air-discharge valve such that the air-discharge valve is temporarily opened in a liquid introducing operation in which the liquid is introduced from the main tank to the liquid-supply pump and an air discharging operation in which air separated from the liquid in the sub-tank by causing the liquid to be flowed through the first channel by driving of the liquid-supply pump is discharged through the third channel, and such that the air-discharge valve is closed in times other than the liquid introducing operation and the air discharging operation.