Conical Nozzle Geometry for Liquid Droplet Ejection
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Solution Overview
Problem
In liquid droplet ejection apparatuses, pointed-end ejection from nozzles leads to irregular droplet formation and ejection angle deviations, causing image quality deterioration due to high viscosity resistance, particularly in nozzles with cylindrical shapes on the ejection side.
Innovation Solution
The design incorporates a conical portion with a gradually decreasing diameter and a cylindrical portion connected smoothly, optimizing the nozzle's internal structure to reduce viscosity resistance and improve ejection accuracy by adjusting the axial lengths and taper angles of these portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a cylindrical-shaped nozzle portion is used on the ejection side, then the manufacturing is simplified, but the viscosity resistance increases causing pointed-end ejection and ejection angle deviation
Solution Approach 1:
The patent applies curvature by replacing the cylindrical nozzle portion with a conical portion that has a gradually changing cross-sectional area. This curved geometry (tapered shape) reduces viscosity resistance and prevents pointed-end ejection, thereby improving ejection accuracy while maintaining manufacturing feasibility through standard conical machining processes.
Solution Approach 2:
The patent changes the geometric parameters of the nozzle by introducing a conical portion with specific taper angles (30-60 degrees) and length-to-diameter ratios (0.5-2.0). This parameter optimization reduces viscosity resistance and prevents ejection anomalies, resolving the contradiction between manufacturing simplicity and ejection reliability.
2Reliability
If the nozzle has a large taper angle to reduce viscosity resistance, then pointed-end ejection is prevented, but ejection bending increases reducing image quality
Solution Approach 1:
The patent optimizes the taper angle parameter within a specific range (30-60 degrees) to balance two competing requirements: a sufficiently large angle to reduce viscosity resistance and prevent pointed-end ejection, but not so large as to cause excessive ejection bending. This parameter optimization resolves the contradiction between droplet formation quality and ejection angle accuracy.
Solution Approach 2:
The patent introduces a dynamic balance in the nozzle design by considering the interaction between liquid viscosity, pressure, and geometric parameters. The conical portion's dimensions are optimized to dynamically adapt to the liquid properties and ejection conditions, achieving both good droplet formation and accurate ejection angles.
3Reliability
If the conical portion axial length is increased to reduce viscosity resistance, then pointed-end ejection is prevented, but the device complexity and size increase
Solution Approach 1:
The patent optimizes the conical portion axial length parameter within a specific range (0.5-2.0 times the inner diameter) to achieve the minimum effective length needed to reduce viscosity resistance and prevent pointed-end ejection. This optimized parameter range prevents excessive device complexity and size while maintaining ejection stability.
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 configuration prevents pointed-end ejection and reduces ejection angle deviations, enhancing image quality by ensuring precise droplet formation and improved pumping capability.
Implementation Method 1
a conical portion 23a having an inner diameter which gradually decreases toward the outside; and a cylindrical portion 23b having an inner diameter which is substantially unchanged in the axial direction
Implementation Method 2
an apparatus including a channel having a volume to be changed by a pressure generation element and a nozzle communicating with the channel
Data Source
Figure 1~2
Figure 3(a)~3(b)
Figure 4(a)~4(c)
AI summary
An object of the present invention is to provide a liquid droplet ejection head and a liquid droplet ejection apparatus in which viscosity resistance of a liquid to be ejected is reduced on an ejection side of a nozzle to prevent pointed-end ejection and to improve accuracy of an ejection angle. This object is achieved by the following. That is, a channel 28 having a volume to be changed by a pressure generation element and a nozzle 23 communicating with the channel 28 are included. The inside of the nozzle 23 has a conical portion 23a with a diameter becoming gradually smaller toward an outside, and a cylindrical portion 23b continuous with the conical portion 23a and communicating with the outside. A connecting part of the conical portion 23a to the cylindrical portion 23b has the same opening cross-sectional shape as a connecting part of the cylindrical portion 23b to the conical portion 23a. When an inner diameter of the cylindrical portion 23b is represented by D0, the cylindrical portion 23b has an axial length of 0.1D0 to 0.3D0, and the conical portion 23a has an axial length of 0.6D0 or more and a conical surface in which a generating line has an angle of 6 degrees or more and 15 degrees or less with respect to a nozzle central axis.