Liquid Ejection Head Recovery with Below-Threshold Circulation

Solution Overview

Problem

Ink jet printing apparatuses face issues with ink viscosity increase in ejection ports due to water evaporation, leading to defective ejections and color mixture invasion during recovery operations, which can result in abnormal tonality and reduced productivity.

Innovation Solution

A liquid ejection apparatus with a circulation unit that maintains ink flow velocity below the ejection threshold during recovery operations, combined with parallel preliminary ejection to remove color-mixed ink and foreign substances, ensuring efficient nozzle cleaning without productivity loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the circulation pump is stopped during recovery operation, then color-mixed ink and foreign substances can be removed from the ejection port surface, but ink flow velocity cannot be reduced to prevent deep invasion into the circulation channel

Engineering Contradiction:

Improverecovery operation effectivenessVSAvoidproduction delay

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The circulation flow velocity is reduced to below the ejection threshold before the recovery operation begins, preventing color-mixed ink and foreign substances from invading deep into the circulation channel. This preliminary action ensures that when the recovery operation is performed, contaminants remain on the ejection port surface where they can be effectively removed, while avoiding the need to wait for complete flow cessation.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If waiting time is provided after stopping circulation driving, then circulation flow velocity can be reduced to prevent deep invasion, but recovery operation is delayed and productivity is reduced

Engineering Contradiction:

Improveprevention of deep invasionVSAvoidrecovery operation delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The circulation flow velocity is reduced to below the ejection threshold before the recovery operation begins, preventing color-mixed ink and foreign substances from invading deep into the circulation channel. This preliminary action ensures that when the recovery operation is performed, contaminants remain on the ejection port surface where they can be effectively removed, while avoiding the need to wait for complete flow cessation.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If circulation flow velocity is maintained during recovery operation, then productivity is maintained, but color-mixed ink and foreign substances invade deep into the circulation channel

Engineering Contradiction:

Improverecovery operation timingVSAvoidejection performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The circulation flow velocity is reduced to below the ejection threshold before the recovery operation begins, preventing color-mixed ink and foreign substances from invading deep into the circulation channel. This preliminary action ensures that when the recovery operation is performed, contaminants remain on the ejection port surface where they can be effectively removed, while avoiding the need to wait for complete flow cessation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The circulation flow velocity parameter is changed from above the ejection threshold to below the ejection threshold during the recovery operation period. This parameter change prevents the ejection of ink droplets into the circulation channel while maintaining continuous circulation, thus preventing deep invasion of contaminants without stopping the circulation pump.

Inventive Principle:

Principle #35Parameter changes

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 thickening and foreign substance invasion, maintaining ejection performance and reducing image defects while minimizing downtime.

Implementation Method 1

a pressure difference between two pressure adjustment mechanisms is used to generate a flow of an ink so as to pass through a pressure chamber

Methodology Applied

Scientific EffectPressure difference: Pressure Gradient

Data Source

PatentUS20250222696A1Liquid ejection apparatus and method of controlling liquid ejection apparatus

Publication Date: 2025.07.10 CANON KK

AI summary

A liquid ejection apparatus includes: a liquid ejection head including an ejection port configured to eject a liquid and a pressure chamber communicating with the ejection port; a circulation unit configured to circulate the liquid in the liquid ejection head so as to pass through the; a recovery unit configured to perform a recovery operation of the liquid ejection head at a circulation flow velocity slower than a circulation flow velocity of the circulation unit in a case where the liquid ejection head prints an image on a printing medium; and a control unit configured to control preliminary ejection to eject the liquid that is not used for the printing from the ejection port in parallel with the recovery operation by the recovery unit.