Printhead Sub-Ejection Pulse for Viscosity Uniformity
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Solution Overview
Problem
Inkjet printers with pagewidth printheads face challenges in maintaining uniform ink viscosity across a large array of nozzles, leading to variations in drop ejection characteristics and visible artifacts in printed pages due to temperature-dependent ink viscosity.
Innovation Solution
The implementation of a printhead IC with an array of nozzles and drive circuitry that sends ejection pulses to firing nozzles and sub-ejection pulses to non-firing nozzles to maintain ink temperature uniformity, using temperature sensors to adjust pulse durations and compensate for viscosity differences across the printhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pagewidth printheads with large arrays of nozzles are used to increase print speed, then productivity is improved, but temperature uniformity across nozzles deteriorates leading to viscosity variations
Solution Approach 1:
The patent applies local quality by differentiating the treatment of nozzles based on their firing status. Firing nozzles receive full ejection pulses while non-firing nozzles receive reduced-power sub-ejection pulses. This localized differentiation maintains temperature uniformity across the printhead array, preventing viscosity variations that would otherwise occur in large pagewidth printheads operating at high print speeds.
2Temperature
If sub-ejection pulses are sent to non-firing nozzles to maintain temperature uniformity, then temperature uniformity is improved, but energy consumption increases
Solution Approach 1:
The patent implements partial action by sending sub-ejection pulses to non-firing nozzles that provide just enough thermal energy to maintain temperature uniformity without causing full ink ejection. This partial energization approach balances temperature control requirements with energy efficiency, avoiding the excessive energy consumption that would result from sending full ejection pulses to all nozzles regardless of firing status.
3Manufacturing precision
If temperature compensation is implemented across all nozzles, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the nozzle array into functional groups: firing nozzles and non-firing nozzles. Each group receives appropriately tailored pulse signals (full ejection pulses for firing nozzles, sub-ejection pulses for non-firing nozzles). This segmentation approach enables temperature compensation and uniform drop ejection characteristics without requiring complex individual control of each nozzle, thus managing device complexity while improving manufacturing precision.
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 solution ensures uniform drop ejection characteristics across the printhead, improving print quality by maintaining consistent ink viscosity and temperature across all nozzles.
Implementation Method 1
Each nozzle has a corresponding a heater element that superheats the ink to vaporize surrounding ink to generate the bubble that ejects a drop of ink onto the paper
Implementation Method 2
Heat dissipates into the ink as the heater temperature rises to the bubble nucleation temperature
Data Source
AI summary
A printhead IC comprising: an array of nozzles; and, drive circuitry for receiving print data and sending drive pulses to the nozzles in accordance with the print data; wherein, the drive pulses consist of ejection pulses with sufficient energy to eject printing fluid from the nozzles designated to fire at that time, and sub-ejection pulses with insufficient energy to eject printing fluid from the nozzles not designated to fire at that time.