Asymmetric Restrictor Protrusions for Inkjet Head Backflow Prevention
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Solution Overview
Problem
Conventional piezoelectric inkjet heads experience backflow of ink, leading to unstable ink meniscuses and reduced droplet ejection efficiency due to fixed restrictor structures that fail to balance flow resistance and ink refill requirements.
Innovation Solution
The incorporation of protrusions on the inner surface of restrictors within the inkjet head, which increase flow resistance in the backflow direction while maintaining low resistance for ink refill, preventing backflow and pressure wave transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the restrictor cross section is reduced to prevent backflow, then backflow prevention improves, but ink refill becomes insufficient
Solution Approach 1:
The restrictor structure transitions from a fixed cross-section to a dynamic effective cross-section that changes based on flow direction. During backflow prevention, the protrusion structure reduces the effective cross-section to increase resistance. During ink refill, the flow direction changes allowing greater effective cross-section for sufficient ink supply.
Solution Approach 2:
The restrictor employs an asymmetric protrusion structure where the inner surface features protrusions with specific geometric asymmetry. This asymmetry creates different flow resistance characteristics for opposite flow directions, enabling low resistance for forward ink refill while creating high resistance for backward flow prevention.
2Ease of manufacture
If a fixed restrictor structure is used, then manufacturing simplicity improves, but flow resistance balance between backflow prevention and ink refill deteriorates
Solution Approach 1:
The restrictor structure introduces localized protrusions only at specific positions on the inner surface where flow control is needed, rather than changing the entire restrictor structure. This local modification approach maintains manufacturing simplicity while achieving the complex flow resistance balance function.
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
Effectively prevents backflow and crosstalk between pressure chambers, ensuring stable ink supply and efficient droplet ejection by controlling flow resistance, allowing for smooth ink refill and reduced pressure wave transmission.
Implementation Method 1
a plurality of protrusions formed on an inner surface of the restrictor in a structure suitable to increase a flow resistance of the restrictor when ink flows from the pressure chamber to the manifold through the restrictor
Implementation Method 2
a piezoelectric inkjet head ejects ink using a pressure generated by deforming a piezoelectric material
Implementation Method 3
The vibration plates 12 deform by pressure applied from the piezoelectric actuators 40
Data Source
AI summary
A restrictor with a structure to prevent a back flow of ink and an inkjet head including the restrictor. In the inkjet head, an ink channel is formed in a channel plate, and the ink channel includes an ink inlet, a plurality of pressure chambers, a manifold, a plurality of restrictors respectively connecting the pressure chambers to the manifold, and a plurality of nozzles. Piezoelectric actuators are formed on the channel plate. Each of the restrictors includes a plurality of protrusions formed on an inner surface thereof in a structure suitable to increase a flow resistance of the restrictor when ink flows from the pressure chamber to the manifold through the restrictor. Each of the protrusions includes a first surface facing a flow of ink moving through the restrictor in a direction from the manifold to the pressure chamber, and a second surface facing a flow of ink moving through the restrictor in a direction from the pressure chamber to the manifold. The first surface has a low flow resistance, and the second surface has a high flow resistance. Therefore, a black flow of ink is restricted when ink is ejected, and sufficient ink can be supplied through the restrictor during an ink refill process.