Liquid Ejecting Head Dummy Flow Channel Stress Concentration

Solution Overview

Problem

The existing liquid ejecting heads face issues with cracks in the flow channel formation plate due to thermal stress caused by differences in coefficients of linear expansion between silicon and metal components, leading to ink leakage or intermixing between colors.

Innovation Solution

A liquid ejecting head design with a flow channel formation plate featuring dummy flow channel portions with smaller corner angles and closer to the edge, made of a crystalline base member with close-packed plane surfaces, to concentrate stress and induce cracks preferentially in these areas rather than the common liquid chamber, thereby preventing ink leakage and intermixing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the flow channel formation plate is made of silicon and the nozzle plate is made of metal, then processing precision and manufacturing ease are improved, but thermal stress causes cracks in the flow channel formation plate

Engineering Contradiction:

Improveprocessing precisionVSAvoidcrack resistance

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies local quality by creating a through-hole with a tapered shape that has different structural characteristics at different locations. The end regions have a smaller cross-sectional area compared to the central portion, creating localized stress distribution differences. This allows the structure to have varying mechanical properties in different regions to better withstand thermal stress during adhesive curing.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies preliminary action by pre-forming the tapered shape of the through-hole before the adhesive curing process. This preliminary structural preparation ensures that when thermal stress occurs during subsequent heating, the stress is already distributed in a favorable pattern that prevents crack formation in critical areas.

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If the end regions of the reservoir are formed in a tapered shape, then ink flow smoothness is improved, but stress concentration causes cracks at the tapered portions

Engineering Contradiction:

Improveink flow smoothnessVSAvoidcrack resistance

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The patent applies local quality by creating a through-hole with a tapered shape that has different structural characteristics at different locations. The end regions have a smaller cross-sectional area compared to the central portion, creating localized stress distribution differences. This allows the structure to have varying mechanical properties in different regions to better withstand thermal stress during adhesive curing.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies preliminary action by pre-forming the tapered shape of the through-hole before the adhesive curing process. This preliminary structural preparation ensures that when thermal stress occurs during subsequent heating, the stress is already distributed in a favorable pattern that prevents crack formation in critical areas.

Inventive Principle:

Principle #10Preliminary 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

This design effectively reduces the occurrence of cracks in the flow channel formation plate, preventing ink leakage and intermixing between colors by directing stress to weaker areas, ensuring reliable operation of the liquid ejecting head.

Implementation Method 1

corner portions whose angles are smaller than the corner portions formed in the common liquid chamber... concentrate stress and induce cracks preferentially in these areas

Methodology Applied

Scientific EffectStress concentration:

Implementation Method 2

there are differences in the coefficients of linear expansion between those constituent elements; thus changes in temperature caused by heating and cooling during the affixing can cause the constituent elements to extend and contract relative to each other

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS9272294B2Liquid ejecting head and liquid ejecting apparatus

Publication Date: 2016.03.01 SEIKO EPSON CORP

AI summary

The portions at the circumferential edges of a flow channel formation plate in which the corner portions of a dummy flow channel portion are formed are weaker than other portions, and thus when thermal stress has occurred due to temperature changes when the constituent elements of a flow channel unit are affixed to each other, cracks can be induced preferentially in the weak portion, rather than the other portions, starting from the ends of the corner portions. In particular, although similar corner portions are formed in a common liquid chamber, the intersection angle of the corner portions in the dummy flow channel portion is smaller than the intersection angle of the corner portions in the common liquid chamber, and thus it is easier for stress to concentrate in the corner portions of the dummy flow channel portion.