Laminated Liquid Ejection Head With Dual-Pump Ink Circulation
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Solution Overview
Problem
Existing liquid ejection heads face issues such as ejection failure and concentration changes due to liquid thickening or precipitation near ejection openings, with residual bubbles or foreign substances, and ineffective ink circulation when the system is idle for extended periods.
Innovation Solution
A liquid ejection head design featuring a laminated structure with supply and collection flow paths connected to a common flow path, utilizing multiple pumps to circulate ink efficiently, including a first pump on the print element substrate and a second pump external to the substrate, ensuring continuous ink circulation and prevention of concentration changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a micropump is provided inside the print element substrate to circulate liquid, then liquid circulation is achieved, but ink concentration increases in the common flow path during stopped states
Solution Approach 1:
The flow path is segmented into multiple independent circulation paths: a first circulation path within the print element substrate and a second circulation path outside the substrate. This segmentation allows the common flow path to be served by multiple pumps, preventing ink concentration by providing alternative circulation routes that can flush the common flow path effectively.
Solution Approach 2:
The common flow path is designed to be universally served by multiple pumps (first pump inside the substrate and second pump outside) rather than being served by a single pump. This multi-functionality ensures that the common flow path can be effectively flushed and maintained by multiple circulation sources, preventing ink concentration during stopped states.
2Loss of time
If the system is stopped for a long period, then moisture evaporation causes ink concentration, but driving the micropump cannot decrease ink concentration at the ejection opening
Solution Approach 1:
The system performs preliminary circulation actions using multiple pumps before ejection resumes. By activating both the first pump (inside the substrate) and the second pump (outside the substrate) during stopped states, the system pre-flushes the common flow path and prevents ink concentration from developing, so that when ejection resumes, the ink concentration remains acceptable without requiring preliminary ejection operations.
3Reliability
If multiple pumps are used to circulate liquid between common flow path and pressure chamber, then ink circulation effectiveness is improved, but device complexity increases
Solution Approach 1:
The circulation system is segmented into distinct first and second circulation paths with separate pumps. The first circulation path operates within the print element substrate while the second operates outside, allowing independent control and optimization of each path. This segmentation improves reliability by providing redundant circulation routes while keeping each individual path relatively simple.
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 effectively prevents ejection failures by maintaining ink quality and reducing downtime after prolonged idle periods, ensuring high-quality printing without the need for preliminary ejection operations or cap suction.
Implementation Method 1
a first pump, the first pump being configured to circulate liquid between the common flow path and the pressure chamber
Implementation Method 2
a second pump generates a flow of liquid flowing in an order of the supply flow path, the common flow path, and the collection flow path
Implementation Method 3
the pressure chamber being internally provided with an element configured to generate energy utilized for ejecting liquid from the ejection openings
Data Source
AI summary
A liquid ejection head includes a print element substrate including multiple ejection openings, pressure chambers, a common flow path, and pumps, the pumps being configured to circulate liquid between the common flow path and the pressure chamber; and a flow path member laminated to the print element substrate. The flow path member includes a supply flow path and a collection flow path, the supply flow path being configured to supply liquid to the print element substrate, and the collection flow path being configured to collect liquid that is not ejected. The supply flow path and the collection flow path have liquid connection with the same common flow path. A circulating pump generates a flow of liquid flowing in an order of the supply flow path, the common flow path, and the collection flow path, the circulating pump being provided at a position different from the print element substrate.