Piezoelectric Device Electrode Stiffness Strain Management
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Solution Overview
Problem
Piezoelectric devices, such as liquid ejecting heads, face challenges with cracks and burnout in the piezoelectric body layer due to bending deformation and strain, particularly near the boundary between active and inactive portions of the piezoelectric body layer, especially under high-frequency drive pulses.
Innovation Solution
A piezoelectric device configuration with a substrate having recess portions and a diaphragm, where the second electrode has a higher stiffness of 17,000 N/m or more in the area near the end portion, and its length is equal to or less than the piezoelectric body layer's length, to reduce strain and prevent defects like cracks and burnout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piezoelectric body layer is extended to a position on the outside beyond the opening edge of the pressure chamber to suppress bending deformation, then the occurrence of cracks and burnout is reduced, but strain occurs in the active portion that the second electrode overlaps while no strain occurs in the inactive portion, leading to defects at the boundary portion between active and inactive portions
Solution Approach 1:
The patent applies local quality by making the second electrode have different stiffness characteristics in different areas. Specifically, the second electrode has a first area (far from end portion) and a second area (near end portion), where the second area has higher stiffness (17,000 N/m or more) than the first area. This local variation in stiffness allows the electrode to provide appropriate mechanical support at the boundary portion between active and inactive portions of the piezoelectric body layer, reducing strain concentration and preventing defects while maintaining the benefits of extended configuration.
2Productivity
If high frequency drive pulses are supplied to the piezoelectric body layer to improve ejection performance, then productivity is enhanced, but the strain operation of the active portion has high frequency which increases the likelihood of defects such as cracks and burnout at the boundary portion
Solution Approach 1:
The patent addresses this contradiction by implementing local quality through differentiated stiffness in the second electrode. The second area near the end portion has higher stiffness (17,000 N/m or more) to specifically counteract the high-frequency strain effects at the boundary portion between active and inactive areas, while the first area maintains lower stiffness for normal operation. This allows high-frequency drive pulses to be used for improved productivity without excessive defect formation at vulnerable boundary regions.
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 suppresses the occurrence of cracks and burnout in the piezoelectric body layer, ensuring reliable operation of the piezoelectric actuator by managing strain and maintaining device integrity.
Implementation Method 1
a piezoelectric actuator having a first electrode, a piezoelectric body layer, and a second electrode which are stacked in a first direction
Data Source
AI summary
A piezoelectric device includes a diaphragm provided on a side of one surface of a substrate, and a piezoelectric actuator having a first electrode, a piezoelectric body layer, and a second electrode which are stacked in a first direction on a side of a surface opposite to the substrate of the diaphragm, in which when one area far from an end portion of the second electrode is a first area and one area near the end portion of the second electrode is a second area, of two areas of the second electrode in a second direction intersecting the first direction, the second electrode has a stiffness of 17,000 N/m or more in the second area in the first direction, which is higher than a stiffness in the first area in the first direction, and a length in the second area in the first direction is equal to or less than a length of the piezoelectric body layer in the second area in the first direction.