Liquid Ejection Head Circulation Circuit Design
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Solution Overview
Problem
Liquid ejection heads face issues with high-density liquid portions lingering near ejection orifices, leading to poor image quality, especially under conditions like high temperatures, use of special liquids, or low flow rates, where circulation is insufficient to reduce density effectively.
Innovation Solution
A liquid ejection head design with a circulation circuit that includes independent and common supply paths, where the ejection orifice is positioned between inflow and outflow paths, and the insulating layer is structured to reduce flow resistance by optimizing the distances and positions of openings, allowing efficient circulation and refilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid circulation is implemented to prevent evaporation and maintain liquid quality, then liquid supply stability is improved, but flow path length increases and refilling speed decreases
Solution Approach 1:
The flow path is divided into multiple independent supply paths (first through fourth supply paths) that separately connect to the pressure chamber, allowing parallel liquid supply routes. This segmentation enables efficient circulation while maintaining multiple refilling channels, resolving the contradiction between circulation stability and refilling speed.
Solution Approach 2:
The flow paths are configured to extend in the thickness direction of the substrate rather than only in the plane direction. By utilizing the third dimension (depth/thickness), the flow paths can be shortened while still providing adequate circulation, thereby maintaining refilling speed with improved circulation efficiency.
2Productivity
If flow path length is reduced to improve refilling speed, then refilling efficiency is improved, but liquid circulation effectiveness decreases
Solution Approach 1:
Multiple independent supply paths are provided, each with its own opening in the substrate. This segmentation allows liquid to be supplied through multiple routes simultaneously, maintaining circulation effectiveness even when individual path lengths are reduced for faster refilling.
Solution Approach 2:
The flow paths are positioned at different locations and orientations relative to the pressure chamber. Some paths are optimized for refilling (shorter paths) while others are positioned to enhance circulation patterns. This local optimization allows different regions of the flow path system to serve different functions.
3Reliability
If multiple independent supply paths are provided to improve liquid supply ability, then liquid supply stability is improved, but device complexity increases
Solution Approach 1:
Multiple supply paths share common structural elements including the substrate platform, energy generating elements, and pressure chamber. The flow paths are integrated into the substrate structure rather than being separate components, reducing overall device complexity while maintaining multiple supply routes.
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 reduces the density of highly dense liquid portions near ejection orifices, improving image quality by enhancing liquid circulation and refilling efficiency, even under challenging conditions.
Implementation Method 1
the energy generating element being protected against liquid by an insulating layer formed on the first surface of the substrate
Implementation Method 2
a liquid inflow path running through the substrate and the insulating layer so as to allow liquid to flow into the flow path from the second surface side of the substrate; and a liquid outflow path running through the substrate and the insulating layer so as to allow liquid to flow out from the flow path to the second surface side of the substrate
Implementation Method 3
an energy generating element for generating energy for ejecting liquid from the flow path through the ejection orifice
Data Source
AI summary
A liquid ejection head has on one surface of a substrate a liquid flow path having an ejection orifice and a liquid generating energy generating element while the element is protected against liquid by an insulating layer formed on the surface. The liquid ejection head further has a liquid inflow path and a liquid outflow path each running through the substrate and the insulating layer to circulate liquid. The liquid inflow path and the liquid outflow path each have a first opening on the surface of the substrate and a second opening on the surface of the insulating layer and for each of the liquid inflow and outflow paths, the end on the ejection orifice side of the second opening is located closer to the ejection orifice than the end on the ejection orifice side of the first opening.