Liquid Ejecting Head Diaphragm Stress Redistribution
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Solution Overview
Problem
Liquid ejecting heads, such as ink jet recording heads, experience stress concentration at the boundaries between piezoelectric elements and pressure chambers, leading to cracks and defects due to tear stress at the corners of the diaphragm's arms, which is not unique to ink jet heads and affects other liquid ejecting devices.
Innovation Solution
Incorporating holding members with a width equivalent to or larger than the walls between pressure chambers, and an adhesive agent width equal to or smaller than the walls, reduces the maximum principal stress on the diaphragm's arms, preventing cracking by redistributing stress and moving stress raisers away from the corners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If piezoelectric elements are driven to eject liquid droplets, then liquid ejection function is achieved, but stress concentration occurs at the diaphragm corners causing cracks
Solution Approach 1:
Holding members are introduced as intermediary elements between the piezoelectric elements and the diaphragm arms. These holding members support the diaphragm arms at multiple positions, acting as mediators that distribute the stress caused by piezoelectric element deformation, thereby preventing stress concentration at the diaphragm corners and reducing crack occurrence.
Solution Approach 2:
The holding members provide localized support specifically at the diaphragm arm regions adjacent to the pressure chambers. This local reinforcement strategy targets the specific area experiencing highest stress concentration, enhancing crack resistance where it is most needed without requiring overall structural reinforcement.
2Reliability
If holding members are added to reduce stress concentration, then diaphragm crack resistance is improved, but device complexity increases
Solution Approach 1:
The holding members serve multiple functions simultaneously: they provide mechanical support to the diaphragm arms, distribute stress to prevent cracking, and maintain the structural integrity of the liquid ejecting head. This multi-functionality allows a single structural element to address multiple concerns, reducing the need for additional separate components.
Solution Approach 2:
The holding members are integrated into the existing structure of the liquid ejecting head, combining the support function with the overall housing or substrate. This merging approach incorporates the stress-distributing function into the existing structural framework rather than adding completely separate components, thereby minimizing the increase in device complexity.
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 reduces the maximum principal stress on the diaphragm's arms, preventing cracks and enhancing the durability and reliability of liquid ejecting heads by redistributing stress and reducing the occurrence of defects.
Implementation Method 1
Each piezoelectric element includes a first electrode, a piezoelectric layer above the first electrode, and a second electrode above the piezoelectric layer. When voltage is applied across the first electrode and the second electrode, this type of piezoelectric element experiences stress concentration
Data Source
AI summary
A liquid ejecting head includes a flow channel substrate and piezoelectric elements, with a diaphragm between the piezoelectric elements and the flow channel substrate. The flow channel substrate has pressure chambers lined up in a first direction with walls therebetween. Each piezoelectric element includes a first electrode, a piezoelectric layer and a second electrode. Each piezoelectric element has a piezoelectrically active portion, a region in which the piezoelectric layer is sandwiched between the first electrode and the second electrode, and are provided in regions facing the pressure chambers. The liquid ejecting head further includes holding members joined the diaphragm facing the walls using an adhesive agent. The width of the holding members is equivalent to or larger than the width of the walls. The width of an adhesive agent with which the holding members are joined to the diaphragm is equal to or smaller than the width of the walls.