Liquid Ejection Head with Bidirectional Ink Circulation

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Solution Overview

Problem

Existing liquid ejection apparatuses face challenges in effectively managing bubble accumulation in channels, leading to reduced ejection stability due to unidirectional ink circulation and lack of efficient pressure adjustment mechanisms.

Innovation Solution

A liquid ejection head with a circulation system that includes a supply channel, collection channel, circulation pump, and pressure adjustment units that generate pressures with different signs during forward and backward scans, allowing bi-directional ink flow and pressure regulation to mitigate bubble effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a check valve is equipped in the circulation pump to enable unidirectional ink circulation, then the ink circulation direction is controlled, but bubbles accumulate in channels and ejection stability deteriorates

Engineering Contradiction:

Improveink circulation controlVSAvoidejection stability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent removes the check valve that enforced unidirectional flow and instead uses pressure adjustment units to enable bidirectional ink circulation. This inversion of the flow control mechanism allows ink to flow in both directions, preventing bubble accumulation and improving ejection stability while maintaining circulation control.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If pressure adjustment units are added to enable bidirectional ink flow, then bubble accumulation is reduced and ejection stability improves, but device complexity increases

Engineering Contradiction:

Improveejection stabilityVSAvoidpressure control mechanism

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses pressure adjustment units that change pressure parameters dynamically during forward and backward scans. By adjusting pressure signs based on scan direction, the system enables bidirectional ink flow without requiring complex mechanical structures, thus improving ejection stability while keeping the added complexity manageable.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If unidirectional ink circulation is used with a check valve, then the circulation pump structure is simplified, but the effect of accumulated bubbles cannot be reduced

Engineering Contradiction:

Improvecirculation pump structureVSAvoidbubble accumulation

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent implements periodic bidirectional circulation by adjusting pressure signs based on scan direction (forward scan vs. backward scan). This periodic reversal of flow direction prevents bubbles from accumulating in channels, addressing the harmful effect while keeping the pump structure relatively simple.

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

The solution enhances ejection stability by reducing bubble accumulation and improving ink circulation efficiency, maintaining fluidity and ejection characteristics, and reducing the frequency of ink refill, thus stabilizing the ejection process.

Implementation Method 1

a circulation pump capable of supplying the liquid from the supply channel into the pressure chamber, and collecting the liquid in the pressure chamber through the collection channel

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Implementation Method 2

a first pressure adjustment unit disposed between an outlet channel of the circulation pump and the supply channel and configured to adjust a pressure in the supply channel; a second pressure adjustment unit disposed between an inlet channel of the circulation pump and the collection channel and configured to adjust a pressure in the collection channel

Methodology Applied

Scientific EffectPressure adjustment:

Implementation Method 3

an ejection element configured to generate a pressure for ejecting the liquid in a pressure chamber

Methodology Applied

Scientific EffectPressure generation:

Data Source

PatentUS20250206032A1Liquid ejection head and liquid ejection apparatus

Publication Date: 2025.06.26 CANON KK

AI summary

Provided is a liquid ejection head for ejecting a liquid while being scanned in a main scanning direction, including: a circulation pump capable of supplying the liquid from a supply channel into a pressure chamber, and collecting the liquid in the pressure chamber through a collection channel and sending the liquid to the supply channel; a first pressure adjustment unit disposed between an outlet channel of the circulation pump and the supply channel; a second pressure adjustment unit disposed between an inlet channel of the circulation pump and the collection channel. At least one of the first pressure adjustment unit or the second pressure adjustment unit is configured such that pressures with different signs relative to a pressure at rest are generated in response to a forward scan and a backward scan in the main scanning direction.