Piezoelectric Actuator Neutral Surface Control
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Solution Overview
Problem
In liquid jetting apparatuses, the bending of the actuator at the end portion of the pressure chamber in the longitudinal direction reduces the displacement of the liquid, leading to decreased energy conversion from piezoelectric deformation to actuator displacement, while thinning the insulating film to prevent this bending can compromise the strength of the actuator.
Innovation Solution
A liquid jetting apparatus with a thin-walled portion in the insulating film at the end portion of the pressure chamber, where the piezoelectric film overlaps, to bring the neutral surface closer to the central position of the piezoelectric film, reducing bending while maintaining the strength of the insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the piezoelectric film is sandwiched between electrodes extending beyond the pressure chamber edge, then the actuator displacement at the central portion is improved, but bending occurs at the end portion reducing energy conversion efficiency
Solution Approach 1:
The insulating film thickness is varied locally: it is thinned at the end portion where the piezoelectric film extends beyond the pressure chamber to allow controlled bending, while maintaining standard thickness at the central portion to prevent excessive bending and ensure energy conversion efficiency. This local differentiation of film thickness resolves the contradiction by allowing beneficial bending where needed while preventing harmful bending where not needed.
2Stability of the object's composition
If the insulating film is thinned to prevent bending at the end portion, then actuator shape stability is improved, but the strength of the insulating film is compromised
Solution Approach 1:
The insulating film thickness is selectively reduced only at the end portion where bending occurs, while maintaining adequate thickness at the central portion to ensure structural strength. This localized thinning approach prevents bending at critical areas without compromising the overall strength and integrity of the insulating film structure.
Solution Approach 2:
The thickness parameter of the insulating film is changed from a uniform value to a graded value, being thinner at the end portion and thicker at the central portion. This parameter variation allows the film to accommodate bending stresses at the end while maintaining sufficient strength and rigidity at the central portion.
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 reduces bending at the actuator's end portion, enhancing the conversion of piezoelectric deformation to displacement at the central portion of the pressure chamber, while preventing damage to the insulating film by maintaining its thickness.
Implementation Method 1
when a voltage is applied between the individual electrode and the common electrode, the piezoelectric film sandwiched between the two electrodes contracts due to an inverse piezoelectric effect
Data Source
AI summary
A liquid jetting apparatus includes: a channel substrate having a pressure chamber which is long in a first direction; an insulating film provided on the channel substrate to cover the pressure chamber; a piezoelectric film overlapping with the insulating film and having first and second portions, the first portion overlapping with a central portion of the pressure chamber in the first direction, the second portion extending from the first portion in the first direction beyond the pressure chamber, the first portion having a width in a second direction which is smaller than a width of the pressure chamber in the second direction; a first electrode arranged between the insulating film and the piezoelectric film; and a second electrode facing the first electrode with the piezoelectric film being sandwiched therebetween. The insulating film has a thin-walled portion formed at a portion overlapping with the second portion of the piezoelectric film.