Liquid Discharging Head Pressure Control for Nozzle Cleaning

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Solution Overview

Problem

Existing liquid discharging apparatuses face difficulties in effectively removing adhering matter from nozzle surfaces due to the tendency of adhering matter to intrude into nozzles when air jet cleaning, especially under negative pressure conditions which maintain stable ink flow but hinder removal.

Innovation Solution

A liquid discharging apparatus with a pressure changing unit that alters the pressure in the head to a positive pressure state during cleaning, combined with a suction port spaced away from the discharging port surface, allows for effective removal of adhering matter by preventing its intrusion into the nozzles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If air jet nozzle is used to remove adhering matter from nozzle surface, then cleaning effect is improved, but adhering matter may intrude into the nozzles causing difficulty in removal

Engineering Contradiction:

Improveadhering matter removalVSAvoidadhering matter intrusion into nozzles

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

Instead of using air jet to blow adhering matter away (which causes intrusion), the invention uses suction to draw adhering matter out. The suction port is positioned to create a suction force that pulls adhering matter from the nozzle surface without forcing it into the nozzles, effectively inverting the cleaning approach from positive pressure to negative pressure.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The suction port acts as an intermediary element between the adhering matter and the nozzles. By positioning the suction port at a specific distance from the nozzle surface, it creates a controlled suction field that removes adhering matter without direct contact with the nozzles, preventing intrusion while maintaining cleaning effectiveness.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If negative pressure is maintained in the head, then ink leakage is prevented and stable pressure is maintained, but adhering matter is more likely to intrude into the nozzles

Engineering Contradiction:

Improveink flow stabilityVSAvoidadhering matter intrusion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The suction operation is performed as a preliminary action before the discharging operation. By cleaning the nozzle surface with suction beforehand, adhering matter is removed while the head is still under negative pressure, preventing intrusion during subsequent ink discharge without compromising ink flow stability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The cleaning operation is performed periodically between discharging operations. The pressure in the head is temporarily adjusted to positive pressure during cleaning, then restored to negative pressure for discharging. This periodic switching allows effective cleaning without affecting the overall stability of ink flow during recording operations.

Inventive Principle:

Principle #19Periodic action

3Productivity

If suction port is positioned close to discharging port surface, then adhering matter removal is improved, but risk of intrusion into nozzles increases

Engineering Contradiction:

Improvecleaning efficiencyVSAvoidadhering matter intrusion

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The invention optimizes the distance parameter between the suction port and the discharging port surface. By setting this distance to a specific value (not too close, not too far), the suction force is sufficient to remove adhering matter effectively while preventing intrusion into the nozzles. This parameter optimization balances cleaning efficiency with safety.

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

This solution enables efficient removal of adhering matter from the discharging port surface without compromising the stability of the meniscus, thereby maintaining the discharging performance and preventing ink leakage.

Implementation Method 1

a suction port configured to perform a suction operation for the discharging port surface

Methodology Applied

Scientific EffectSuction: Suction

Implementation Method 2

a pressure changing unit configured to change a pressure in the head

Methodology Applied

Scientific EffectPressure change: Pressure Increase

Data Source

PatentUS10245835B2Liquid discharging apparatus, imprint apparatus, and method of manufacturing a component

Publication Date: 2019.04.02 CANON KK

AI summary

Provided is a liquid discharging apparatus, including: a head having a discharging port surface on which discharging ports are formed, and configured to perform a discharging operation for discharging liquid through the discharging ports; a suction port configured to perform a suction operation for the discharging port surface; a pressure changing unit configured to change a pressure in the head; and a control unit configured to perform the suction operation under a state in which the pressure changing unit has changed the pressure in the head in a positive pressure direction with respect to a pressure that is set during the discharging operation and the suction port is spaced away from the discharging port surface.