Liquid Ejecting Head Asymmetric Flow Path Resistance

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Solution Overview

Problem

Existing liquid ejecting heads face instability in ejection operations due to asymmetry in circulation paths, leading to imbalanced pressure loss and resulting in density unevenness or stripes in images, especially when switching between forward and backward liquid circulation directions.

Innovation Solution

A liquid ejecting head configuration that includes a switching mechanism with on-off valves and pressure regulating mechanisms to manage liquid flow between sub-tanks, ensuring stable circulation and refilling of ink, and a flow path structure with adjusted resistances to maintain balanced pressure distribution during ejection operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If liquid circulation direction is switched between forward and backward directions, then pigment coagulation or sedimentation is prevented in the supply system, but asymmetry of circulation paths results in imbalanced pressure loss and unstable ejection state

Engineering Contradiction:

Improvestability of liquid circulationVSAvoiduniformity of ejection state

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies asymmetry principle by intentionally designing different flow path resistances for the first and second individual flow paths. Specifically, the flow path resistance of the first individual flow path is set to be different from that of the second individual flow path (Claim 1). This asymmetric design compensates for the inherent asymmetry in circulation paths when switching between forward and backward directions, ensuring balanced pressure distribution and stable ejection state in both circulation directions.

Inventive Principle:

Principle #4Asymmetry

2Manufacturing precision

If liquid is circulated through individual flow paths with different diameters or flow resistances, then pressure distribution can be balanced during ejection operations, but the complexity of flow path design and manufacturing increases

Engineering Contradiction:

Improveuniformity of pressure distributionVSAvoidsimplicity of flow path structure

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent applies local quality principle by making specific portions of the flow paths have different characteristics. The first and second individual flow paths are designed with different flow path resistances at specific locations (Claim 1). This localized differentiation in flow path resistance allows balanced pressure distribution during ejection operations while keeping the overall flow path structure relatively simple and manageable.

Inventive Principle:

Principle #3Local quality

3Reliability

If fresh ink is regularly supplied to individual flow paths, then ink deterioration is suppressed, but the complexity of the circulation system increases

Engineering Contradiction:

Improvefreshness of ink in ejection portsVSAvoidcomplexity of circulation system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies segmentation principle by dividing the circulation system into multiple individual flow paths (first and second individual flow paths) that are independently controllable (Claim 1). Each individual flow path can be independently circulated, allowing fresh ink to be regularly supplied to each ejection port while maintaining a relatively simple overall system structure through modular design.

Inventive Principle:

Principle #1Segmentation

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 stabilizes liquid circulation and refilling processes, preventing coagulation or sedimentation of pigments and maintaining consistent ejection performance regardless of circulation direction, thereby reducing density unevenness and stripe issues in printed images.

Implementation Method 1

the asymmetry of circulation paths may result in an imbalanced pressure loss in ejection operation

Methodology Applied

Scientific EffectPressure loss: Pressure Drop

Implementation Method 2

circulating liquid through a plurality of individual flow paths

Methodology Applied

Scientific EffectFluid flow:

Implementation Method 3

coagulation or sedimentation of the pigment

Methodology Applied

Scientific EffectCoagulation: Coagulation

Implementation Method 4

coagulation or sedimentation of the pigment

Methodology Applied

Scientific EffectSedimentation: Sedimentation

Data Source

PatentEP3461642B1Liquid ejecting head and liquid ejecting apparatus

Publication Date: 2022.04.13 CANON KK

Figure 1A~1B
Figure 2A~2B
Figure 3

AI summary

The liquid ejecting head (300) comprises a first individual flow path (28) and a second individual flow path (29) for supplying liquid to a pressure chamber (30), a first common flow path (18) for supplying liquid in common to the plurality of first individual flow paths, (28) and a second common flow path (19) for supplying liquid in common to the plurality of second individual flow paths (29). A first circulation for causing liquid to flow in the order of the first individual flow path, (28) the pressure chamber (30), and the second individual flow path (29) and second circulation for causing liquid to flow in the reverse order of the first circulation are switched. A flow path resistance of the first common flow path (18) is designed to be less than a flow path resistance of the second common flow path (19) and a flow path resistance of the first individual flow path (28) is designed to be less than a flow path resistance of the second individual flow path (29).