Liquid Ejection Head Layout for Thermal Ink Circulation Stability
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Solution Overview
Problem
Existing liquid ejection heads face challenges in maintaining circulation efficiency and flow amount while minimizing substrate and head size, as well as preventing ink evaporation and concentration at ejection ports, which can lead to instability and increased viscosity.
Innovation Solution
A liquid ejection head design with individual ejection units featuring first and second energy generation elements disposed to intersect ejection port arrays, and resistance structures in flow paths to manage circulation flow, reducing substrate size and stabilizing ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a differential pressure scheme is used to circulate ink, then ink circulation is achieved, but the sizes of the recording device main body and the head increase due to pressure adjustment mechanisms and pumps
Solution Approach 1:
The patent extracts the circulation function from a separate pump system and integrates it into the head itself using a thermal circulation mechanism. The circulation flow path is formed within the head substrate, and a circulation heater provides the driving force, eliminating the need for external pumps and pressure adjustment mechanisms in the head structure.
Solution Approach 2:
The patent replaces the mechanical pump-based differential pressure system with a thermal field-based circulation system. The circulation heater generates thermal energy that creates natural convection currents in the ink, substituting mechanical pumping with thermal-driven fluid motion, thereby reducing mechanical components and head size.
2Reliability
If the circulation flow path is extended to improve circulation efficiency, then ink circulation improves, but the substrate size increases
Solution Approach 1:
The patent utilizes the vertical dimension (thickness direction) of the head substrate to route the circulation flow path. Instead of extending the path horizontally across the substrate surface, the flow path travels through the thickness of the substrate, allowing efficient circulation within a compact planar footprint and reducing the substrate area required.
Solution Approach 2:
The circulation flow path is nested within the head substrate structure itself, utilizing the internal volume and thickness of the substrate. The ejection energy generation elements are also integrated within the same substrate, creating a compact nested arrangement that maximizes circulation efficiency without increasing substrate area.
3Reliability
If ink is circulated to prevent evaporation and concentration, then ejection stability improves, but device complexity increases due to additional energy generation elements and flow path structures
Solution Approach 1:
The head substrate serves multiple functions: it provides the structural foundation, contains the ejection energy generation elements for droplet ejection, incorporates the circulation flow path for ink circulation, and houses the circulation heater for thermal-driven flow. This multi-functional integration reduces overall device complexity by combining multiple systems into a single unified structure.
Solution Approach 2:
The patent merges the ejection system and circulation system into a single integrated head structure. The circulation flow path is formed within the same substrate that contains the ejection ports and energy generation elements, and the circulation heater is integrated with the existing thermal management structure, combining previously separate functions into one unified device.
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 maintains circulation efficiency and flow amount, stabilizes ejection, and minimizes ink discarding, enhancing throughput and image quality by curbing evaporation and concentration at ejection ports.
Implementation Method 1
first energy generation elements that are provided in the pressure chambers and generate heat energy for ejecting the liquid from the ejection ports
Implementation Method 2
second energy generation elements that are provided in the individual flow paths and generate heat energy
Implementation Method 3
the individual flow paths are provided with resistance structures that increase a flow resistance between the first energy generation elements and the second energy generation elements
Data Source
AI summary
A liquid ejection head including: individual ejection units that include ejection ports, pressure chambers, first energy generation elements that are provided in the pressure chambers and generate heat energy, and second energy generation elements that are provided in individual flow paths and generate heat energy; and a common flow path that supplies a liquid to the individual flow paths, a direction in which the ejection ports are aligned perpendicularly intersecting an extending direction of the individual flow paths, the liquid ejection head being provided with a structure in which a flow resistance between the first energy generation elements and the second energy generation elements is increased is used.