Piezoelectric Actuator Electrode Design for Stress Reduction
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Solution Overview
Problem
Piezoelectric actuators in liquid transfer devices face issues with large stress generation, which can lead to cracks and degradation of dielectric strength, particularly at the connection portions where the piezoelectric layers are sandwiched between electrodes.
Innovation Solution
A piezoelectric actuator design where the first and second piezoelectric layers are not sandwiched between the drive electrodes at the connection portion, using a configuration with three types of drive electrodes to prevent stress generation, and an insulating layer and shielding electrode to manage potential differences and maintain the flow passage unit at a stable potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the piezoelectric layers are sandwiched between drive electrodes at the connection portion, then the electric field can be generated uniformly across the entire piezoelectric layer, but large stress is generated in the piezoelectric layer at the connection portion
Solution Approach 1:
The patent applies local quality by making the electrode arrangement non-uniform: at the connection portion, only one drive electrode is provided while the piezoelectric layer is not sandwiched between two electrodes, preventing stress generation in this critical region. At other portions, both drive electrodes are provided to generate the necessary electric field for actuation. This localized differentiation resolves the contradiction between uniform field generation and stress prevention.
2Power
If the piezoelectric layers are sandwiched between drive electrodes, then the piezoelectric actuator can be driven effectively, but cracks may form in the piezoelectric layers due to large stresses
Solution Approach 1:
The patent makes the electrode configuration location-dependent: at the connection portion where stress would be problematic, the sandwiched structure is avoided to prevent crack formation. At other portions where actuation is needed, both drive electrodes are provided to generate sufficient electric field for effective driving. This resolves the contradiction between driving capability and structural integrity.
Solution Approach 2:
The patent introduces an insulating layer as an intermediary element in the electrode configuration. The insulating layer is positioned between the drive electrode and the piezoelectric layer at the connection portion, preventing direct contact and thus preventing stress-induced crack formation while still allowing the actuator to function. This intermediary resolves the contradiction by decoupling the driving function from the stress-generating contact.
3Reliability
If the piezoelectric layers are not sandwiched between drive electrodes at the connection portion, then stress and crack formation are prevented, but the electric field generation may be affected
Solution Approach 1:
The patent accepts non-uniform electric field generation as a necessary compromise: at the connection portion, electric field generation is sacrificed to ensure reliability and prevent cracks. At other portions, full electric field generation is maintained for actuation. The overall system reliability is improved by protecting the critical connection portion, and the actuator still functions through the electric field generated at non-connected portions.
4Reliability
If three types of drive electrodes are used to prevent stress generation, then the piezoelectric layer reliability is improved, but the device complexity increases
Solution Approach 1:
The patent uses local quality to justify the increased complexity: the three-type electrode configuration (both electrodes, one electrode, or no electrode) is applied locally at different portions of the piezoelectric actuator. This localized differentiation, while increasing overall device complexity, is necessary to prevent stress-induced failures at the connection portion while maintaining actuation capability at other portions. The complexity is concentrated only where needed for reliability.
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
Prevents large stress generation and crack formation in the piezoelectric layers and vibration plate, enhancing the dielectric strength and maintaining reliable ink ejection properties by avoiding unnecessary deformation and potential-induced adverse effects.
Implementation Method 1
a piezoelectric actuator driven by deforming a piezoelectric layer
Implementation Method 2
an insulating layer and shielding electrode to manage potential differences and maintain the flow passage unit at a stable potential
Data Source
AI summary
A vibration plate, an insulating layer and a plurality of piezoelectric layers, connected to each other, are connected to an upper face of a flow passage unit. Between the plurality of piezoelectric layers, there is provided an intermediate electrode having: opposing portions opposed to center portions of pressure chambers; and connecting portions for connecting the opposing portions at a region opposed to connection portion with the flow passage unit. Between the insulating layer and one of the piezoelectric layers, there is provided a lower electrode extending across the entire region not opposed to the intermediate electrode, including regions opposed to regions of the pressure chambers located outside the center portions thereof. At an upper face of the other piezoelectric layer, upper electrodes are located to be opposed to the pressure chambers. A shielding electrode is arranged between the vibration plate and the insulating layer across the entire regions thereof.