Piezoelectric Actuator Active Portion Extension for Ink Droplet Weight
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Solution Overview
Problem
Existing liquid ejecting apparatuses face challenges in controlling the initial deflection of vibration plates in piezoelectric actuators, leading to inconsistent ink droplet ejection and increased stress on the vibration plate, which can result in breakage, especially when trying to widen the pressure chamber to increase droplet weight.
Innovation Solution
A liquid ejecting apparatus with a piezoelectric actuator design where the active portion extends from the edge portion to the outside of the pressure chamber, utilizing a drive signal with contraction and expansion elements to control the pressure chamber volume, eliminating the need for initial deflection control and reducing stress on the vibration plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the pressure chamber is widened to increase the weight of the ejected liquid droplet, then the droplet weight increases, but the stress on the vibration plate increases and the vibration plate becomes more easily broken
Solution Approach 1:
The patent extends the active portion of the piezoelectric actuator from the edge portion of the pressure chamber to the outside of the pressure chamber in the planar direction. This dimensional extension allows the actuator to generate sufficient displacement without widening the pressure chamber, thereby increasing droplet weight indirectly through improved actuator efficiency rather than chamber size expansion.
Solution Approach 2:
The patent introduces a drive signal with contraction and expansion elements that dynamically changes the volume of the pressure chamber. By controlling the vibration plate to contract and expand the pressure chamber volume, the system achieves greater displacement amplitude without increasing the maximum chamber dimensions, thus avoiding increased stress on the vibration plate while still enabling heavier droplet ejection.
2Shape
If a member having compressive stress is introduced into the vibration plate to achieve convex initial deflection, then the initial deflection can be controlled, but it cannot be said that the initial deflection is necessarily deformed to be convex toward the pressure chamber side and control remains difficult
Solution Approach 1:
The patent replaces the mechanical approach of introducing compressive stress members to control initial deflection with an electrical control approach. By using a drive signal with contraction and expansion elements applied to the piezoelectric actuator, the system dynamically controls the vibration plate shape and pressure chamber volume, achieving reliable convex deflection control through electrical signals rather than mechanical stress introduction.
3Shape
If a member having patterned tensile stress is disposed in the vibration plate to achieve convex initial deflection, then the initial deflection can be controlled, but the tensile stress is further increased by displacement generated when an electric field is applied to the piezoelectric actuator, so that the piezoelectric actuator is easily broken
Solution Approach 1:
The patent eliminates the need for patterned tensile stress members by extracting this unnecessary component from the system. The convex initial deflection is achieved not through mechanical stress introduction but through the inherent properties of the piezoelectric actuator combined with the drive signal control, thereby removing the source of excessive tensile stress that would otherwise compromise piezoelectric actuator reliability.
Solution Approach 2:
The patent provides beforehand cushioning by using the contraction element in the drive signal to prepare the pressure chamber in a contracted state before the expansion phase. This pre-positioning reduces the displacement range required during operation, thereby reducing the stress experienced by the piezoelectric actuator during normal operation and preventing actuator breakage.
4Device complexity
If the active portion of the piezoelectric actuator is provided only at the edge portion of the movable region, then the central portion remains exposed, but the displacement amount of the piezoelectric actuator is limited
Solution Approach 1:
The patent segments the active portion of the piezoelectric actuator into two functional zones: one at the edge portion of the movable region that interfaces with the pressure chamber, and another extending to the outside of the pressure chamber. This segmentation allows different portions of the active region to contribute differently to the overall displacement, achieving greater total displacement while maintaining structural simplicity.
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 design enhances the displacement amount of the piezoelectric actuator, improves pressure chamber disposition density, and allows for increased ink droplet weight without widening the pressure chamber, reducing the risk of vibration plate breakage and enabling high-density nozzle arrangements.
Implementation Method 1
a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode that are formed on a surface side of the vibration plate opposite to the flow path formation substrate
Data Source
AI summary
A liquid ejecting apparatus includes: a liquid ejecting head that includes a flow path formation substrate in which a pressure chamber communicating with a nozzle is formed, a vibration plate, and a piezoelectric actuator having a first electrode, a piezoelectric layer, and a second electrode; and a drive unit that supplies a drive signal for driving the piezoelectric actuator, in which the piezoelectric actuator includes an active portion, the active portion is extended from an edge portion, which is a region other than a central portion of a region facing the pressure chamber, to the outside of the pressure chamber, and the drive signal includes a contraction element that contracts the pressure chamber from a reference volume of the pressure chamber when no electric field is applied to the piezoelectric layer, and an expansion element that expands the pressure chamber contracted by the contraction element.