Inkjet Nozzle Failure Detection Using Mask Pattern
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Solution Overview
Problem
Existing inkjet print head systems face challenges in detecting nozzle failures quickly and efficiently, as the time required to sense and analyze residual pressure waves is lengthy, making real-time detection for each ejection unit during printing impractical due to computational power constraints and potential for visible artifacts in single-pass processes.
Innovation Solution
A method involving a mask pattern with evenly distributed blank pixels allows for rapid nozzle failure detection during printing, using a detection waveform that does not eject droplets, enabling quick assessment of ejection unit malfunctions and minimizing artifacts by ensuring detection occurs without impacting image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If residual pressure wave sensing and analysis is performed for each ejection unit after each droplet ejection, then nozzle failure detection precision is improved, but the time required for detection increases and computational power requirements become prohibitively high
Solution Approach 1:
The patent extracts only the essential detection information needed for nozzle failure detection from the residual pressure wave, rather than performing complete analysis. By focusing on specific characteristics (amplitude, decay rate) rather than full wave analysis, the system achieves adequate detection precision with significantly reduced computational requirements and faster processing time.
Solution Approach 2:
The patent performs partial sensing of the residual pressure wave characteristics - measuring only the essential parameters (amplitude, decay rate) rather than complete wave analysis. This partial action provides sufficient information for failure detection while dramatically reducing the time and computational resources required compared to full analysis.
2Reliability
If detection frequency is increased to detect failures immediately, then reliability of detection is improved, but the number of blank pixels increases creating visible artifacts
Solution Approach 1:
The patent applies local quality by concentrating detection efforts at strategically positioned blank pixels distributed across the image rather than uniformly across all pixels. This allows sufficient detection coverage for reliability while minimizing the total number of blank pixels to avoid visible artifacts.
Solution Approach 2:
The patent implements periodic detection at regular intervals through the mask pattern rather than continuous detection at every pixel. This periodic sampling maintains adequate detection reliability while significantly reducing the number of blank pixels compared to uniform high-frequency detection.
3Measurement precision
If detection waveform amplitude is increased to improve signal sensitivity, then measurement precision is improved, but droplet ejection occurs creating printing errors
Solution Approach 1:
The patent changes the parameters of the detection waveform - using optimized amplitude and duration values that generate sufficient pressure fluctuation for sensitive measurement while remaining below the threshold that would cause droplet ejection. This parameter optimization enables precise measurement without creating printing errors.
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 fast and frequent nozzle failure detection, allowing for immediate compensation and reducing the likelihood of visible artifacts, even in single-pass processes, by ensuring detection occurs shortly after failure occurrence and maintaining image quality through minimal and imperceptible blank pixel placement.
Implementation Method 1
A well-known electromechanical transducer is a piezo-actuator, comprising two electrodes and a layer of piezo-electric material arranged therebetween. When an electric field is applied by application of a voltage over the electrodes, the piezo-material mechanically deforms and the deformation of the piezo-actuator generates the pressure wave in the liquid.
Implementation Method 2
measuring the pressure fluctuation in order to detect the malfunction state
Data Source
Figure 1
Figure 2
Figure 3(A)~3(B)
AI summary
A method of nozzle failure detection in an ink jet printer having a plurality of ejection units (E) each of which comprises a nozzle (14) and an associated liquid chamber with an electromechanical transducer for energizing a pressure wave in the liquid chamber so as to expel an ink droplet from the nozzle (14), the method comprising steps of nozzle failure detection to be performed, for each ejection unit, with a given minimum detection frequency, wherein each nozzle failure detection step comprises: -energizing the transducer with a waveform that does not lead to the ejection of a droplet but creates a pressure fluctuation that is sensitive to whether or notthe ejection unit is in a malfunction state; and -measuring the pressure fluctuation in order to detect the malfunction state, the method comprising: -defining a mask pattern (22) that is independent of image contents to be printed, said mask pattern defining positions of blank pixels (24) on a dark background (26) such that the blank pixels are evenly distributed over an area of an image (20), wherein one blank pixel occurs in each pixel column printed with one of the nozzles (14);and -when an image is being printed, performing the nozzle failure detection steps for each ejection unit at timings at which the respective nozzles (14) are in pixel positions that belong to the mask pattern (22).