Piezoelectric Actuator with Selective Electrode Adhesion
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Solution Overview
Problem
Conventional piezo actuators experience mechanical stresses due to inactive zones where internal electrodes do not fully penetrate the electrical field, leading to damage and reduced performance.
Innovation Solution
A fully active piezo actuator design where internal electrodes extend to the outer side and have alternating regions with poor and good adhesion to a coating, allowing for reliable contact with external electrodes without inactive zones, reducing mechanical stresses through a method involving specific electrode pastes and a DLC coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If internal electrodes are shortened to create inactive zones for electrical insulation, then electrical insulation between internal electrodes and external electrodes is improved, but mechanical stresses increase and piezo stack damage occurs
Solution Approach 1:
The internal electrodes are designed with spatially varying adhesion properties: regions adjacent to external electrodes have poor adhesion (first regions) to allow coating removal and electrical contact, while other regions have good adhesion (second regions) to maintain structural integrity and reduce mechanical stresses during operation
Solution Approach 2:
The internal electrodes are divided into functionally distinct regions: first regions with poor coating adhesion for electrical contact purposes, and second regions with good coating adhesion for mechanical support. This segmentation allows each region to fulfill its specific function optimally
2Strength
If internal electrodes extend to the outer side of the piezo stack, then inactive zones are eliminated and mechanical stresses are reduced, but electrical insulation between internal and external electrodes becomes problematic
Solution Approach 1:
A coating is applied to the outer side of the piezo stack before assembling external electrodes. This coating serves as a preliminary insulating barrier that prevents electrical contact between internal electrodes and external electrodes, while allowing the internal electrodes to extend fully to the outer side for mechanical stress reduction
Solution Approach 2:
The coating acts as an intermediary layer between the internal electrodes and external electrodes. It provides electrical insulation where needed (in second regions with good adhesion) while allowing controlled removal in first regions to establish electrical contact, thus mediating between the conflicting requirements of insulation and contact
3Reliability
If a coating is applied to the outer side of the piezo stack for insulation, then electrical insulation is improved, but manufacturing complexity increases due to selective coating removal
Solution Approach 1:
The internal electrodes are designed with spatially varying adhesion properties: regions adjacent to external electrodes have poor adhesion (first regions) to allow coating removal and electrical contact, while other regions have good adhesion (second regions) to maintain structural integrity and reduce mechanical stresses during operation
Solution Approach 2:
The coating removal process is facilitated by the inherent poor adhesion of the first regions of internal electrodes to the coating. This self-service property allows selective coating removal without requiring complex masking or etching processes, simply by applying mechanical or chemical removal methods that exploit the adhesion difference
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 solution effectively reduces mechanical stresses during operation, enabling a longer service life and cost-effective production of piezo actuators by ensuring all internal electrodes make contact with external electrodes, eliminating inactive zones.
Implementation Method 1
The function of a piezo element is based on the deformation of piezoceramic materials such as, for example, lead-zirconate-titanate, under the action of an electrical field. If an electrical voltage is applied to the piezo element, it expands in the perpendicular direction with respect to the electrical field which is generated (inverse piezo effect).
Implementation Method 2
each have a first region which adheres poorly, or does not adhere, to a coating, and a second region which adheres well to the coating
Data Source
AI summary
A fully active piezoelectric stack has alternately successive piezoelectric layers and inner electrodes which pass through to the outer side of the stack and each have a first region, which does not adhere or adheres poorly and a second region which adheres well to the coating. The inner electrodes are provided for the purpose of using their first regions to alternately contact-connect a first outer electrode and a second outer electrode. The outer side of the fully active piezoelectric stack is coated with the coating at least in regions which are assigned the outer electrodes. The coating is then removed in regions which border the first regions of the inner electrodes and the two outer electrodes are applied to the remaining coating, with the result that the outer electrodes contact-connect the first regions of the inner electrodes and the coating is otherwise arranged between the inner electrodes and the outer electrodes.