Piezoelectric Droplet Ejection Head Shear Deformation Control
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Solution Overview
Problem
Existing droplet ejection methods, such as inkjet recording heads, face challenges in suppressing the bending of droplet tails during ejection, which affects landing accuracy and requires high precision in nozzle inner surface shape, making it difficult to maintain stable ejection without reducing drive frequency.
Innovation Solution
A control method for droplet ejection heads using piezoelectric materials, where channels are divided into groups and driven sequentially with specific voltage pulses to cause shear deformation, ensuring the droplet is ejected without tail bending by optimizing the volume changes and meniscus manipulation, thus avoiding the need for additional pulses that reduce drive frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a second pulse is applied to protrude the meniscus before droplet separation, then tail bending is suppressed, but drive frequency is reduced
Solution Approach 1:
The invention applies a preliminary action by protruding the meniscus before droplet separation using a carefully timed voltage pulse. The pulse is applied during a specific time window (0.5-2.0 ms before separation) to advance the meniscus position, which prevents tail bending without requiring an additional separate pulse, thus maintaining drive frequency
Solution Approach 2:
The invention changes the timing parameter of the voltage pulse application rather than adding a new pulse. By controlling the pulse to be applied 0.5-2.0 ms before droplet separation, the meniscus protrusion is achieved at the optimal moment, suppressing tail bending while keeping the drive cycle intact and frequency maintained
2Reliability
If a voltage pulse is applied to cancel residual pressure wave, then stable ejection is achieved, but drive frequency is reduced
Solution Approach 1:
The invention merges the function of canceling residual pressure wave with the main ejection pulse. The voltage pulse is designed to simultaneously accomplish both droplet ejection and residual wave cancellation, eliminating the need for a separate cancellation pulse and maintaining drive frequency
Solution Approach 2:
The single voltage pulse applied to the piezoelectric element serves multiple functions: it protrudes the meniscus, separates the droplet, and cancels the residual pressure wave. This multi-functionality eliminates additional pulses that would reduce drive frequency while ensuring stable ejection
3Stability of the object's composition
If nozzle inner surface accuracy is increased, then tail bending is suppressed, but manufacturing difficulty increases
Solution Approach 1:
The invention replaces the mechanical approach of achieving precise nozzle inner surface geometry with a field-based approach using piezoelectric actuation. The piezoelectric element dynamically controls the meniscus position and droplet formation, compensating for nozzle imperfections without requiring high-precision mechanical manufacturing
Solution Approach 2:
Instead of changing the physical geometry of the nozzle (which would require high-precision manufacturing), the invention changes the operational parameters by applying controlled voltage pulses to the piezoelectric element. This dynamic parameter control achieves stable droplet ejection regardless of nozzle inner surface accuracy
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 method allows for stable droplet ejection with minimal tail bending, maintaining high drive frequency and improved landing accuracy without the need for precise nozzle shape maintenance or additional pulse applications.
Implementation Method 1
the sidewall comprising at least partially a piezoelectric material... by a pressure generated with the shear deformation liquid in a channel is ejected as a droplet from a nozzle
Data Source
AI summary
A driving method of a droplet ejection head having plural channels separated by sidewalls formed with piezoelectric material, the channels being divided into three groups; and an electric voltage pulse is applied to each of the groups sequentially in a time-sharing mode, and to generate a shear deformation of the sidewall, and liquid is ejected as a droplet from a nozzle, wherein applying process of the pulse includes: a first step for enlarging a volume of a channel; a second step for keeping the enlarged volume; a third step for reducing the volume; a fourth step for keeping the reduced volume; and a fifth step for enlarging the volume, wherein the third step starts when α/β≦⅓ is satisfied for the protruded pillar at an adjoining channel nozzle driven just before; where α denotes a width of the pillar, and β denotes a maximum width of the pillar.