Inkjet Back Pressure Control for Dripping and Bubble Prevention

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Solution Overview

Problem

Inkjet printing devices face issues with ink dripping and air bubble entry during the ink circulation stop period due to shifts in back pressure and condensation on the jetting surface, leading to jetting failures and incomplete ink absorption.

Innovation Solution

A printing device with a controller that adjusts the back pressure of the inkjet head at the start of the ink circulation stop period based on the set input value, using a table or expression associating the ink circulation stop period with the back pressure, to maintain a negative pressure level that suppresses ink dripping and air bubble entry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the ink circulation is stopped during printing device stop, then energy consumption is reduced, but ink adhering to the nozzle tends to dry and back pressure shifts to positive pressure causing ink dripping

Engineering Contradiction:

Improveenergy consumptionVSAvoidink jetting reliability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The circulation unit operates periodically rather than continuously - it stops during printing device stop to save energy, then operates again before and during printing to restore and maintain proper back pressure levels, preventing ink drying and dripping while reducing overall energy consumption

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The circulation unit operates in advance before printing starts to restore the back pressure to the appropriate negative level, ensuring that when printing begins, the ink jet head is already in the optimal pressure state for reliable jetting without ink dripping or drying

Inventive Principle:

Principle #10Preliminary action

2Object-affected harmful factors

If a cap covers the jetting surface to suppress drying, then ink drying is prevented, but ink dripping occurs due to condensation and meniscus swelling

Engineering Contradiction:

Improveink dryingVSAvoidink dripping

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The back pressure parameter is dynamically adjusted to a negative level that counteracts the effects of condensation and meniscus swelling caused by cap coverage, maintaining the ink in a stable state that prevents both drying and dripping simultaneously

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system monitors the back pressure level and uses this feedback to control the circulation unit, adjusting the pressure to maintain it within the appropriate negative range that prevents both ink drying and ink dripping under cap coverage conditions

Inventive Principle:

Principle #23Feedback

3Reliability

If the circulation unit operates continuously, then back pressure is maintained, but energy consumption increases

Engineering Contradiction:

Improveback pressure stabilityVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The circulation unit automatically activates based on the printing device state - it operates when the device is running or about to run, and stops when the device is stopped, self-regulating its operation to maintain back pressure only when necessary for printing operations

Inventive Principle:

Principle #25Self-service

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

The solution effectively prevents ink dripping and air bubble entry, ensuring reliable operation by maintaining a controlled back pressure that balances the risk of ink drying and bubble ingress, thus enhancing the operational stability of the inkjet head.

Implementation Method 1

a circulation unit that circulates the ink in the ink circulation flow passage

Methodology Applied

Scientific EffectFluid circulation:

Implementation Method 2

a first pressurization unit that pressurizes an inside of the ink storage unit to a first pressure

Methodology Applied

Scientific EffectPressure application: Pressurisation

Implementation Method 3

a moisturizing cap that stores a cap liquid and covers the jetting surface to form a moisturizing space between the moisturizing cap and the jetting surface

Methodology Applied

Scientific EffectCondensation: Condensation

Implementation Method 4

a first pressurization unit that pressurizes an inside of the ink storage unit to a first pressure higher than a pressure in the ink storage unit during a printing operation of jetting the ink to a printing medium by the inkjet head in a case of wiping

Methodology Applied

Scientific EffectPressure application: Pressurisation

Data Source

PatentEP4074511B1Printing device and back pressure control method

Publication Date: 2024.09.11 FUJIFILM CORP

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AI summary

A printing device includes an ink jet head that jets an ink from a jetting surface, an ink circulation flow passage through which the ink circulates, a moisturizing unit that moisturizes the jetting surface in an ink circulation stop period in which circulation of the ink in the ink circulation flow passage is stopped, a reception unit that receives a set input value of the ink circulation stop period, and a controller that controls a back pressure of the ink jet head at a start of the ink circulation stop period in accordance with the set input value of the ink circulation stop period received by the reception unit.