Piezoelectric Liquid Discharge Head Film Layout for Crack Resistance
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Solution Overview
Problem
Existing liquid discharge heads face challenges in preventing piezoelectric actuator breakage due to cracks and dielectric breakdown, which are difficult to screen and occur at varying timings, while maintaining displacement efficiency.
Innovation Solution
A protective film is strategically applied to stress-concentrated areas of the piezoelectric actuator, covering parts of the gap region between the piezoelectric body and the liquid chamber periphery, without significantly reducing displacement efficiency, thereby enhancing stress resistance and preventing cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective film is applied to the entire piezoelectric actuator, then reliability is improved by preventing cracks, but displacement efficiency deteriorates due to restricted piezoelectric body deformation
Solution Approach 1:
The protective film is selectively applied only to the end surface and lateral surfaces of the piezoelectric actuator, excluding the top surface that contacts the diaphragm. This localized protection prevents cracks in stress-concentrated areas while maintaining displacement efficiency by allowing full deformation of the piezoelectric body during operation.
Solution Approach 2:
The protective film coverage is segmented into specific regions: the end surface, lateral surfaces, and corner portions are protected, while the top surface is left exposed. This segmentation allows the protective function to be applied where most needed (stress-concentrated areas) without interfering with the functional deformation area.
2Reliability
If the piezoelectric actuator is designed with larger gap regions for stress relief, then reliability is improved, but device complexity increases due to additional protective film application requirements
Solution Approach 1:
The protective film is applied with varying coverage to different regions: full coverage on the end surface and lateral surfaces, partial coverage on corner portions, and no coverage on the top surface. This localized quality approach provides enhanced protection where stress concentrates while maintaining simplicity in the overall design.
3Reliability
If the protective film covers corner portions of the piezoelectric actuator, then reliability is improved by preventing crack initiation, but manufacturing precision requirements increase
Solution Approach 1:
The protective film is applied in advance to cover the corner portions and other stress-concentrated areas before the piezoelectric actuator is assembled into the liquid discharge head. This preliminary protection prevents crack initiation at vulnerable corners during subsequent manufacturing and assembly processes, reducing the need for high-precision positioning during final assembly.
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 protective film effectively prevents cracking of the piezoelectric actuator under high loads without impairing the displacement efficiency, ensuring reliable operation even after one trillion vibrations.
Implementation Method 1
a piezoelectric actuator on the diaphragm, the piezoelectric actuator including a piezoelectric body configured to deform the diaphragm in response to a drive voltage applied to the piezoelectric body
Data Source
AI summary
A liquid discharge head includes: a nozzle plate including a nozzle; a liquid chamber substrate having an individual chamber; a diaphragm; a piezoelectric actuator including a piezoelectric body, a wiring portion covering a first region of the piezoelectric actuator; and a protective film covering a second region of the piezoelectric actuator other than the first region. A first outer periphery of the piezoelectric body in the second region is interior of a second outer periphery of the individual chamber in the second region. A gap region between the first outer periphery and the second outer periphery has: a first gap region having a first width in the longitudinal direction; and a second gap region having a second width in a transverse direction orthogonal to the longitudinal direction, the second width larger than the first width. The protective film covers a part of the first gap region in the second region.