Inkjet Head Through Hole Design for Low-Viscosity Ink Stability
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Solution Overview
Problem
Conventional shear mode inkjet heads struggle with ink overflow when using low-viscosity ink, leading to unstable ink ejection due to inadequate flow path resistance in through holes, which can result in ejection failures during high driving cycles.
Innovation Solution
The inkjet head incorporates a through hole design with a constricted portion having a smaller cross-sectional area than the end portions, providing a flow path resistance of 0.2 or higher, which restricts ink overflow and ensures stable ejection of low-viscosity ink by improving ink introducing performance and bubble removability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the flow path resistance of through holes is increased to restrict ink overflow, then ink overflow is reduced, but ink supply into the through holes is delayed which may lead to ejection failure in high driving cycles
Solution Approach 1:
The through hole is designed with non-uniform cross-sectional area, featuring a constricted portion with smaller area between the end portions. This local variation in geometry creates different flow resistance characteristics at different locations within the same through hole, allowing the system to achieve both overflow restriction and adequate ink supply
Solution Approach 2:
The flow path resistance of the through hole is specifically controlled to be 0.2 or higher by adjusting the geometric parameters of the through hole, particularly the cross-sectional area distribution along its length. This parameter optimization enables the system to prevent ink overflow while maintaining reliable ink supply for ejection
2Ease of manufacture
If a conventional through hole design is used, then manufacturing is simple, but ink overflow occurs with low-viscosity ink leading to unstable ejection
Solution Approach 1:
The through hole geometry is optimized by controlling the cross-sectional area distribution, specifically incorporating a constricted portion with smaller area. This geometric parameter change achieves stable ink ejection by preventing overflow while maintaining manufacturability through standard sandblasting processes
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 design enables stable ejection of low-viscosity ink even during high driving cycles, preventing ink overflow and maintaining ink introducing performance while preventing pressure wave attenuation and refilling issues.
Implementation Method 1
flow path resistance of the through hole is a value of 0.2 or higher
Implementation Method 2
a through hole forming process of sandblasting both surfaces of a board main body of the board to form the through hole
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An inkjet head includes a head chip 1 including a driving channel 11a and a nozzle 21 ejecting ink in the driving channel 11a and provided on a surface of a driving wall facing an inside of the driving channel 11a with a driving electrode 13 and a wiring board 3 connected to a rear surface of the head chip 1 to cover the driving channel 11a. The wiring board 3 is provided at a position thereof corresponding to the driving channel 11a with a through hole 31 adapted to introduce ink into the driving channel 11a. A constricted portion having a smaller cross-sectional area than those of the end portions is formed between end portions of the through hole 31 in an ink introducing direction, and flow path resistance of the through hole 31 is a value of 0.2 or higher. Accordingly, even low-viscosity ink can be ejected in a stable manner.