Liquid Ejecting Head Thermal Expansion Matching
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Solution Overview
Problem
Existing liquid ejecting heads face reliability issues due to residual stress caused by differences in thermal expansion between communication substrates and case heads, which are adhered using thermoset adhesives, leading to reduced performance and accuracy.
Innovation Solution
A liquid ejecting head design where the supply path member, made from synthetic resin, has a higher linear expansion coefficient than the flow path member, and is heated using a heater to reduce residual stress, with optional temperature sensors and control sections to maintain constant expansion and minimize stress fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thermoset adhesive is used to join the communication substrate and case head, then strong bonding strength is achieved, but residual stress arises due to differential thermal contraction reducing reliability
Solution Approach 1:
The invention changes the temperature parameter by heating the supply path member (case head) to a temperature where its linear expansion coefficient matches that of the communication substrate. This parameter adjustment prevents differential thermal contraction and eliminates residual stress, allowing strong bonding with thermoset adhesive while maintaining reliability
Solution Approach 2:
The invention performs preliminary heating of the supply path member before the bonding process. By pre-heating the case head to achieve thermal expansion coefficient matching, the residual stress problem is prevented before bonding occurs, rather than attempting to address it after assembly
2Reliability
If the supply path member is made from synthetic resin with high linear expansion coefficient, then residual stress is reduced through differential expansion, but material selection freedom is limited
Solution Approach 1:
The invention changes the temperature parameter dynamically to adjust the linear expansion coefficient of the synthetic resin supply path member. By controlling temperature, the same material can achieve different expansion coefficients, providing both reliability through stress reduction and versatility in material selection
Solution Approach 2:
The invention uses synthetic resin as a composite material solution that combines the benefits of high linear expansion coefficient (for stress reduction) with temperature controllability. The synthetic resin case head serves multiple functions: structural support, thermal expansion matching through temperature control, and cost-effective manufacturing
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 enhances the reliability of the liquid ejecting head by reducing residual stress and improving the accuracy and quality of ink droplet placement, while allowing for cost-effective material selection for the supply path member.
Implementation Method 1
A linear expansion coefficient of the supply path member is greater than a linear expansion coefficient of the flow path member. The flow path member and the supply path member are joined together by a thermoset adhesive. The heater is provided to the supply path member.
Implementation Method 2
The communication substrate and the case head are heated in cases in which a thermoset adhesive is employed to adhere the communication substrate and the case head to each other
Data Source
AI summary
A liquid ejecting head includes a nozzle that ejects a liquid, a flow path member formed with a flow path that guides the liquid to the nozzle, a supply path member formed with a supply path that supplies the liquid to the flow path member, and a heater that heats the supply path member. A linear expansion coefficient of the supply path member is greater than a linear expansion coefficient of the flow path member. The flow path member and the supply path member are joined together by a thermoset adhesive. The heater is provided to the supply path member.