Jetting Device Filter Obstruction Detection via Acoustic Impedance
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Solution Overview
Problem
Inkjet printers face instability in droplet generation due to filter clogging, which causes a pressure drop in the ink duct, especially when multiple nozzles are fired simultaneously, leading to inadequate ink supply and poor printing quality.
Innovation Solution
A simplified filter status detection system that measures electric responses after actuation of the transducer to analyze time-dependent pressure fluctuations, allowing for the assessment of filter obstruction without requiring a specific pressure drop detector, utilizing existing electronic circuitry for impedance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter is used to prevent contaminants from entering ejection units, then printing reliability is improved, but the filter may become clogged over time causing pressure drop and droplet generation instability
Solution Approach 1:
The system continuously monitors the acoustic wave characteristics and uses this feedback to detect filter obstruction status. The control unit adjusts operating parameters based on the detected changes in acoustic wave patterns, enabling real-time compensation for filter clogging effects and maintaining stable droplet generation.
Solution Approach 2:
Instead of using a mechanical pressure sensor or flow meter to detect filter status, the patent uses acoustic wave measurement and electrical impedance detection. The acoustic wave properties (amplitude, frequency, decay rate) serve as indicators of filter obstruction, replacing complex mechanical measurement systems with simpler acoustic and electrical sensing.
2Measurement precision
If a dedicated pressure drop detector is added to monitor filter status, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The existing acoustic wave measurement circuitry, originally designed for monitoring droplet ejection process, is made multi-functional by also using it to detect filter obstruction status. The same sensors and signal processing units serve dual purposes: monitoring acoustic wave characteristics for quality control and detecting changes in wave patterns to identify filter clogging, eliminating the need for separate dedicated detectors.
Solution Approach 2:
The system uses its own operational parameters (acoustic wave characteristics) to self-diagnose filter status. By analyzing changes in the acoustic wave patterns that are naturally generated during normal operation, the system can detect filter obstruction without requiring external testing equipment or separate measurement systems.
3Productivity
If multiple nozzles are fired simultaneously to improve printing speed, then productivity is improved, but ink consumption increases causing faster filter clogging
Solution Approach 1:
The system performs preliminary detection of filter obstruction status by continuously monitoring acoustic wave characteristics before complete clogging occurs. By detecting early signs of filter loading through changes in acoustic wave amplitude and frequency, the system can alert users or adjust parameters proactively, extending the effective operational life of the filter and reducing unexpected downtime.
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 approach enables continuous monitoring of filter status during operation, ensuring stable droplet generation by adjusting voltage pulse amplitude based on detected wave patterns, thereby maintaining print quality and preventing clogging-related issues.
Implementation Method 1
The electro-mechanical transducer may for example be a piezoelectric transducer. When a voltage pulse is applied to the transducer, this will cause a mechanical deformation of the transducer. As a consequence, an acoustic pressure wave is created in the liquid ink in the duct
Implementation Method 2
an acoustic pressure wave is created in the liquid ink in the duct, and when the pressure wave propagates to the nozzle, an ink droplet is expelled from the nozzle
Implementation Method 3
a filter arranged to filter the liquid being supplied into the duct
Implementation Method 4
the impedance of the transducer is changed when the body of the transducer is deformed or exposed to an external mechanical strain, the impedance can be used as a measure of the reaction forces which the liquid in the duct exerts upon the transducer
Data Source
Figure 1
Figure 2A~2B
Figure 3~5
AI summary
A jetting device comprising an ejection unit arranged to eject a droplet of a liquid and comprising a nozzle (22), a liquid duct (16) connected to the nozzle (22), and an electro- mechanical transducer (26) arranged to create an acoustic pressure wave in the liquid in the duct, the device further comprising a filter (32) arranged to filter the liquid being supplied into the duct (16), and a filter status detection system (48, 50, 52) arranged to detect an obstruction status of the filter (32) by measuring a property of the liquid in the duct (16), characterized in that the filter status detection system (48, 50, 52) comprises a circuit configured for measuring the electric response of the transducer (26), for recording changes in the electric response that represent pressure fluctuations induced by the acoustic wave in the form of a time-dependent function, and for judging the obstruction status of the filter on the basis of that function.