Liquid Ejection Head Bypass Circulation for Stable Ink Supply
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Solution Overview
Problem
Existing liquid ejection apparatuses face issues with ejection stability due to the one-directional circulation of ink, leading to decreased ink supply to ejection ports when the ejection volume increases, as seen in Japanese Patent Laid-Open No. 2014-195932, where the circulation pump with a check valve does not allow ink to be supplied through ink collection channels.
Innovation Solution
A liquid ejection head design incorporating a pressure chamber, upstream and downstream channels, a pump, an inflow channel, and a bypass channel that allows part of the liquid to flow from the upstream channel into the pressure chamber through the downstream channel, enabling bidirectional ink circulation within the head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a check valve is installed in the circulation pump to enable one-directional circulation, then the circulation reliability is improved, but the ink supply volume to ejection ports decreases when ejection volume increases
Solution Approach 1:
The patent removes the check valve from the circulation pump and inverts the circulation logic by using the pressure differential between pressure chambers to drive bidirectional circulation. Ink flows from high-pressure chambers through downstream channels to the pump, then through upstream channels to low-pressure chambers, creating a natural reverse-flow circulation system that increases ink supply volume while maintaining circulation reliability.
Solution Approach 2:
The system transitions from static one-directional circulation with a check valve to dynamic bidirectional circulation where flow direction changes based on pressure differential. The circulation pump dynamically adjusts ink flow direction and volume in response to varying ejection demands, allowing the system to adapt ink supply volume to match ejection volume requirements.
2Device complexity
If ink circulation is restricted to one direction through check valve, then the circulation system complexity is reduced, but the ejection stability deteriorates when ejection volume increases
Solution Approach 1:
Instead of using a check valve to enforce one-directional flow, the patent inverts the approach by removing the check valve and using pressure differential to naturally drive bidirectional flow. This inversion maintains system simplicity while improving ejection stability through enhanced ink supply capability that adapts to varying ejection volumes.
Solution Approach 2:
The system implements pressure differential feedback where ink flow direction and volume are automatically regulated by pressure differences between pressure chambers. When ejection volume increases, pressure differential increases, driving greater ink flow through the bidirectional circulation system, thereby maintaining ejection stability without complex control mechanisms.
3Quantity of substance
If bidirectional ink circulation is implemented, then the ink supply volume and ejection stability are improved, but the device complexity increases due to additional channels and pump configuration
Solution Approach 1:
The circulation pump serves multiple functions: it drives ink circulation, regulates ink flow volume, and enables bidirectional flow control. The upstream and downstream channels serve dual purposes as both circulation paths and pressure equalization routes. This multi-functionality achieves bidirectional circulation with enhanced ink supply volume while minimizing additional structural complexity.
Solution Approach 2:
The bidirectional circulation system uses the inherent pressure differential between pressure chambers to drive ink flow, eliminating the need for complex external control mechanisms. The system self-regulates flow direction and volume based on pressure conditions, achieving improved ink supply capability without proportionally increasing device complexity.
4Device complexity
If ink is only supplied through upstream channels from the pump, then the circulation control is simplified, but the ink supply sufficiency decreases when ejection volume increases
Solution Approach 1:
The patent removes the conventional unidirectional pump control and inverts the flow path by enabling ink to naturally flow from downstream to upstream channels through pressure differential. This creates a dual-path supply system where ink reaches pressure chambers through both upstream and downstream channels, doubling the effective ink supply volume while maintaining simple circulation control based on pressure equilibrium.
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 configuration maintains ink stability and ejection quality by preventing thickening and deposition of ink components, reduces apparatus size and cost, and simplifies the scanning mechanism by eliminating the need for ink collection channels, thus enhancing ejection performance and apparatus efficiency.
Implementation Method 1
a pump which communicates with the upstream channel and the downstream channel and is configured to cause the liquid in the downstream channel to flow into the upstream channel
Implementation Method 2
a pressure chamber in which a pressure generated by an ejection element configured to generate the pressure is exerted, wherein the pressure is for ejecting a liquid from an ejection port
Data Source
AI summary
A liquid ejection head includes a pressure chamber, an upstream channel, a downstream channel, a pump, an inflow channel, and a bypass channel. The upstream channel communicates with the pressure chamber to supply the liquid to the pressure chamber. The downstream channel communicates with the pressure chamber. The pump communicates with the upstream channel and the downstream channel to cause the liquid in the downstream channel to flow into the upstream channel. The inflow channel communicates with the upstream channel to cause the liquid to be supplied to the pressure chamber to flow into the upstream channel. The upstream channel and the downstream channel communicate with each other through the bypass channel without the pressure chamber being between the upstream channel and the downstream channel. Part of the liquid flowing from the upstream channel into the bypass channel flows into the pressure chamber through the downstream channel.