Piezoelectric Element Electrode Orientation for Stress Management
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Solution Overview
Problem
Existing liquid ejection heads using piezoelectric elements often experience breakage due to stress at the boundary between movable and non-movable portions, particularly when the first electrode crosses the short side of the pressure chamber, leading to deformation and potential burnout of the piezoelectric material layer.
Innovation Solution
The design includes a configuration where the extracting portion electrically connecting the piezoelectric element to external wiring crosses the long side of the pressure chamber, allowing stress to be absorbed or dispersed, and ensuring a larger movable portion within the piezoelectric material layer, thereby preventing breakage. Additionally, the first electrode is formed inside the second electrode, allowing for easier vibration and individual control of each piezoelectric element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the first electrode crosses the short side of the pressure chamber in a plan view, then the piezoelectric element can be electrically connected to external wiring, but stress concentrates at the boundary between movable and non-movable portions causing piezoelectric material layer breakage
Solution Approach 1:
The patent inverts the conventional configuration by having the extracting portion cross the long side of the pressure chamber instead of the short side. This inversion changes the orientation of stress concentration from the short-side boundary to the long-side boundary, where the vibration plate's deformation characteristics better accommodate the stress, preventing piezoelectric material layer breakage while maintaining electrical connectivity.
2Ease of operation
If the extracting portion crosses the short side of the pressure chamber, then electrical connection is achieved, but the vibration plate's deformation is suppressed leading to stress concentration and piezoelectric material breakage
Solution Approach 1:
The patent changes the geometric parameter of the extracting portion's orientation from crossing the short side to crossing the long side of the pressure chamber. This parameter change alters the stress distribution pattern in the piezoelectric material layer, allowing stress to be distributed along the long side where the vibration plate's deformation characteristics provide better stress absorption, thereby maintaining strength.
3Adaptability or versatility
If the first electrode is formed inside the second electrode, then individual control of each piezoelectric element is enabled, but the movable portion area is reduced potentially affecting vibration efficiency
Solution Approach 1:
The patent applies local quality by making the first electrode individually formed for each piezoelectric element while keeping it inside the second electrode. This configuration provides individual control capability for each element. The movable portion area is maintained sufficiently large by optimizing the electrode dimensions and positioning, ensuring that each piezoelectric element can effectively vibrate while being individually controllable.
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 effectively prevents the breakage of the piezoelectric material layer and allows for easier vibration of the vibration portion, enhancing the reliability and performance of the liquid ejection head by distributing stress more effectively and allowing for individual control of each piezoelectric element.
Implementation Method 1
a piezoelectric element in which a piezoelectric material layer is formed between a first electrode that is individually formed for each of a plurality of piezoelectric elements and a second electrode that is formed across the plurality of piezoelectric elements
Data Source
AI summary
A liquid ejection head includes a vibration portion that serves as a wall of a pressure chamber having a shape extending in a first direction; at least one piezoelectric element that is disposed on the vibration portion at an opposite side to the pressure chamber; and an extracting portion that electrically connects the piezoelectric element to external wiring. The piezoelectric element includes a first electrode, a second electrode, and a piezoelectric material layer between the first electrode and the second electrode. In a plan view, the first electrode has a planar shape that is included in shapes of the second electrode and the pressure chamber, and the extracting portion protrudes from a peripheral edge of the first electrode so as to cross a long side of an inner peripheral edge extending in the first direction of the pressure chamber.