Piezoelectric Diaphragm Bending Rigidity Ratio for Crack Prevention
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Solution Overview
Problem
Liquid ejecting apparatuses, such as piezoelectric ink jet printers, face challenges in maintaining diaphragm reliability due to potential cracking issues over long-term use, which affects the apparatus's performance and durability.
Innovation Solution
The design incorporates a diaphragm with a piezoelectric element and a partition wall, where the first and second electrode layers, along with the piezoelectric layer, are laminated in a specific order, and the pressure chamber has an elongated shape. The active and non-active portions of the diaphragm have distinct bending rigidities, with a bending rigidity ratio of EI1/EI2 ≤ 40, to reduce stress and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diaphragm structure is made more rigid to prevent cracking, then reliability improves, but displacement amount decreases
Solution Approach 1:
The patent applies local quality by creating different bending rigidities in different portions of the diaphragm. The active portion (where piezoelectric element is located) has different bending rigidity compared to the non-active portion. This allows the active portion to be sufficiently rigid to prevent cracking while maintaining adequate displacement in the non-active portion, thus resolving the contradiction between reliability and displacement amount.
Solution Approach 2:
The patent changes the bending rigidity parameter by controlling the thickness and material composition of the diaphragm in different regions. By adjusting these parameters to achieve a specific bending rigidity ratio (EI1/EI2) between active and non-active portions, the patent optimizes both reliability and displacement performance simultaneously.
2Reliability
If the bending rigidity ratio EI1/EI2 is reduced to prevent cracking, then reliability improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent establishes a specific parameter range (EI1/EI2 ≤ 40) for the bending rigidity ratio to balance reliability improvement with manufacturability. This quantitative guideline allows manufacturers to control the bending rigidity through standard thickness and material selection without requiring excessive precision, thus resolving the contradiction between reliability and manufacturing precision.
Solution Approach 2:
The patent employs composite material structures for the diaphragm, combining layers with different material properties to achieve the desired bending rigidity ratio. This approach allows flexible control of mechanical properties through material composition rather than requiring extremely precise dimensional control, thereby reducing manufacturing precision requirements while maintaining reliability.
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 configuration enhances the reliability of the liquid ejecting head by reducing the likelihood of diaphragm cracking, thereby improving the apparatus's longevity and performance, while also increasing the displacement amount of the diaphragm.
Implementation Method 1
a piezoelectric element disposed on the first surface... the piezoelectric element includes a first electrode layer, a piezoelectric layer, and a second electrode layer
Data Source
AI summary
A liquid ejecting head in which a first electrode layer, a piezoelectric layer, and a second electrode layer of a piezoelectric element are laminated, a pressure chamber, which is partitioned by a partition wall, has an elongated shape, in a structure including the diaphragm and the piezoelectric element including an active portion and a non-active portion lateral direction, a first position is a position on an inner side of the active portion when viewed in the thickness direction, a second position is a position on an inner side of the non-active portion and closest to a boundary between the pressure chamber and the partition wall, and EI1/EI2≤40, wherein EI1 is a bending rigidity of the active portion at the first position and EI2 is a bending rigidity of the non-active portion at the second position.