Electromechanical Transducer Electrode Configuration for Charge Distribution

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Solution Overview

Problem

Existing electromechanical transducer elements face challenges in maintaining stable polarization states and durability due to heat history effects and excessive charge injection during the polarization process, leading to depolarization and insulation breakdown.

Innovation Solution

The design incorporates a specific configuration of electrodes and insulation protection membranes with L-shaped fifth electrodes surrounding individual electrode pads to evenly distribute charges and prevent concentration, allowing for uniform charge injection and improved polarization stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a metal electrode (Pt) is used as the lower electrode, then electrical conductivity is improved, but fatigue characteristics of PZT are degraded due to Pb diffusion

Engineering Contradiction:

Improvefatigue characteristics of PZTVSAvoidPb diffusion

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

An oxide electrode (SrRuO3) is introduced as an intermediary layer between the PZT piezoelectric body and the metal electrode. This intermediate oxide electrode prevents direct contact between Pb in PZT and the metal electrode, thereby blocking Pb diffusion while maintaining electrical conductivity. The oxide electrode acts as a protective barrier that resolves the contradiction between conductivity and fatigue resistance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If high voltage is applied repeatedly to align polarization directions, then polarization stability is improved, but insulation breakdown occurs due to excessive charge injection

Engineering Contradiction:

Improvepolarization stabilityVSAvoidinsulation breakdown

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent applies different treatment to different regions of the electrode structure. The oxide electrode is specifically designed with particular thickness and material properties in regions adjacent to the piezoelectric body to control charge injection locally. This localized quality control allows polarization alignment while preventing excessive charge accumulation that would cause insulation breakdown.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the material parameter of the electrode from pure metal to oxide material (SrRuO3), and controls the thickness parameter of the oxide electrode layer. These parameter changes enable the electrode to perform dual functions: facilitating polarization alignment through controlled charge injection while preventing excessive charge accumulation through material properties, thereby avoiding insulation breakdown.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If individual electromechanical transducer elements are formed for each pressure generation chamber, then discharge precision is improved, but device complexity increases

Engineering Contradiction:

Improvedischarge precisionVSAvoidstructure complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent segments the electromechanical transducer into independent elements, with each element having its own piezoelectric body and electrode structure. This segmentation allows each element to be precisely controlled for individual pressure generation chambers, improving discharge precision. The modular segmented structure enables independent optimization of each element while maintaining overall system functionality.

Inventive Principle:

Principle #1Segmentation

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 enhances the electromechanical transducer element's durability and maintains stable ink discharge characteristics by reducing charge concentration and insulation breakdown, enabling high-density arrangement and efficient ink discharge.

Implementation Method 1

an electromechanical transducer element 106 such as a piezoelectric element

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS9168744B2Electromechanical transducer element, method of manufacturing the same, liquid droplet discharge head, and liquid droplet discharge device

Publication Date: 2015.10.27 RICOH CO LTD

AI summary

An electromechanical transducer element includes a substrate; a first electrode formed on the substrate as a common electrode; an electromechanical transducer membrane formed on the first electrode; a second electrode formed on the electromechanical transducer membrane as an individual electrode; a first insulation protection membrane formed on the first and the second electrode; a third electrode electrically connected to the first electrode; a fourth electrode electrically connected to the second electrode; a second insulation protection membrane including a common electrode pad formed on the third electrode and plural individual electrode pads formed on the fourth electrode; and a fifth electrode formed so as to surround a vicinity of at least one of the individual electrode pads disposed at end parts.Further, the fifth electrode is formed on the first insulation protection membrane and is electrically connected to the first electrode.