Thermal Inkjet Printhead De-Clog Pulse Control

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Solution Overview

Problem

Inkjet printers face issues with nozzle clogging due to increased ink viscosity during periods of inactivity, leading to inefficient printhead maintenance and frequent cartridge replacement, as water evaporation raises ink viscosity, preventing bubble formation and ink ejection.

Innovation Solution

The implementation of a printhead IC with an array of nozzles and drive circuitry that operates in two modes: printing and maintenance modes, where de-clog pulses with longer durations are used to clear clogs, and temperature sensors adjust drive pulses based on ink viscosity to optimize ink ejection, and an open actuator test circuitry to identify defective nozzles for maintenance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the printhead is left idle during periods of inactivity, then energy consumption is reduced, but ink viscosity increases due to water evaporation causing nozzle clogging

Engineering Contradiction:

Improveenergy consumptionVSAvoidnozzle functionality

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The system performs preliminary heating action during idle periods by applying low-power pulses to the heater elements before actual printing begins. This preliminary action prevents ink viscosity increase and nozzle clogging by maintaining the ink in a fluid state without requiring full printing operation, thus resolving the contradiction between energy saving and nozzle reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system changes the operational parameters of the heater elements by switching from high-power printing pulses to low-power maintenance pulses during idle periods. This parameter change allows the system to maintain ink fluidity and prevent clogging while significantly reducing energy consumption, addressing both concerns simultaneously

Inventive Principle:

Principle #35Parameter changes

2Reliability

If traditional vacuum suction maintenance is used to clear clogged nozzles, then nozzle clogging is removed, but large volumes of ink are wasted requiring frequent cartridge replacement

Engineering Contradiction:

Improvenozzle functionalityVSAvoidink consumption

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The system changes the maintenance approach by using controlled thermal heating instead of vacuum suction. By adjusting heater power and pulse duration parameters, the system can precisely control the heating process to clear clogs without requiring large volumes of ink, thus reducing ink waste while maintaining nozzle functionality

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system replaces the mechanical vacuum suction method with a thermal heating approach. This substitution eliminates the need for high-volume ink suction and allows for more precise, controlled maintenance that clears clogs through thermal expansion and viscosity reduction rather than mechanical force, significantly reducing ink consumption

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If high-power printing pulses are used to ensure reliable ink ejection, then printing reliability is improved, but heat loss into the ink increases reducing printing efficiency

Engineering Contradiction:

Improveink ejection reliabilityVSAvoidheat loss into ink

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The system uses periodic pulse delivery instead of continuous high-power heating. By timing the high-power printing pulses to occur only when needed for actual ink ejection, and using low-power maintenance pulses during idle periods, the system maintains reliable ink ejection while minimizing heat loss into the ink through reduced overall thermal energy input

Inventive Principle:

Principle #19Periodic action

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 effectively prevents nozzle clogging by using longer de-clog pulses and adjusts drive pulses based on ink viscosity, reducing maintenance needs and extending printhead operational life by ensuring consistent ink ejection and minimizing cartridge replacement.

Implementation Method 1

These have a small heater element associated with each nozzle that superheats the ink for form a vapor bubble

Methodology Applied

Scientific EffectSuperheating: Superheating

Implementation Method 2

superheats the ink for form a vapor bubble

Methodology Applied

Scientific EffectVapor bubble formation: Phase Change

Implementation Method 3

The vapor bubble creates pressure pulse in the ink that ejects a drop through the nozzle

Methodology Applied

Scientific EffectPressure pulse: Pressure Increase

Implementation Method 4

During periods of inactivity, water can evaporate from the ink in the nozzles

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentUS7604321B2Thermal inkjet printhead with de-clog firing mode

Publication Date: 2009.10.20 MEMJET TECH LTD

AI summary

A printhead IC comprising: an array of nozzles, each with a corresponding heater to form a vapor bubble in printing fluid that causes a drop of the printing fluid to eject through the nozzle; and, drive circuitry for generating drive pulses that energize the heaters, the drive circuitry being configured to operate in two modes, a printing mode in which the drive pulses it generates are printing pulses, and a maintenance mode in which the drive pulses are de-clog pulses; wherein, the de-clog pulse has lower power and a longer duration than the printing pulse.