Hermetically Sealed Piezo Actuator with Water-Consuming Medium
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Solution Overview
Problem
Piezoceramic multilayer actuators experience increased conductivity and leakage current due to water vapor penetration, which is not effectively addressed by existing technologies, especially in applications requiring long-term operation without property changes.
Innovation Solution
A hermetically sealed housing with a water-consuming medium that absorbs and chemically converts water, combined with glass or ceramic bushings for electrical connections, prevents water vapor from causing increased conductivity and leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If polymeric coatings are used to protect actuator surfaces, then mechanical protection is provided, but water vapor penetrates the coating leading to increased conductivity and leakage current
Solution Approach 1:
A hermetically sealed housing acts as an intermediary barrier between the actuator and the environment, completely preventing water vapor penetration while maintaining mechanical protection. The housing encapsulates the actuator, creating a sealed environment that eliminates the harmful effects of moisture without compromising structural integrity.
Solution Approach 2:
The hermetically sealed housing creates an inert environment around the actuator, isolating it from reactive water vapor in the atmosphere. This sealed enclosure effectively replaces the harmful atmospheric environment with a controlled, moisture-free internal environment, preventing electrochemical reactions at the actuator surface.
2Reliability
If ceramic coatings or glass are used as cover, then water vapor penetration is reduced, but microcracks form during operation allowing moisture penetration
Solution Approach 1:
The protective system is segmented into multiple components: a hermetically sealed housing structure with separate sealing elements and connection points. This segmentation allows the housing to maintain its sealed integrity even when subjected to thermal expansion or mechanical stress, preventing microcrack formation while maintaining water vapor resistance.
Solution Approach 2:
The housing incorporates flexible sealing elements and expansion joints that can accommodate thermal expansion and mechanical stress without forming microcracks. These flexible components maintain the hermetic seal integrity under varying operating conditions, preventing moisture penetration while allowing for dimensional changes.
3Adaptability or versatility
If expansion joints are provided in housing base and cover, then actuator expansion is accommodated, but moisture penetration paths are created
Solution Approach 1:
Expansion joints are constructed using flexible, hermetically sealed components that can accommodate thermal expansion and mechanical movement while maintaining moisture barrier integrity. The flexible sealing elements deform elastically to allow dimensional changes without creating permanent openings or penetration paths for moisture.
Solution Approach 2:
The expansion joint system uses composite construction combining rigid structural elements with flexible sealing materials. This composite design provides both the mechanical strength to accommodate expansion and the sealing capability to prevent moisture penetration, resolving the contradiction between adaptability and harmful factor resistance.
4Reliability
If hermetic sealing with welding is used, then water vapor penetration is prevented, but manufacturing complexity increases
Solution Approach 1:
The design uses standardized, pre-manufactured hermetic sealing components that can be efficiently assembled through welding. While welding adds a manufacturing step, the use of simple, standardized housing geometries and off-the-shelf sealing elements minimizes overall complexity and maintains ease of manufacture while achieving reliable hermetic sealing.
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 results in extremely low leakage currents even under prolonged operation with nominal field strength, reducing leakage current by about 1,000,000 times compared to unencapsulated actuators.
Implementation Method 1
a water-consuming medium 21 is introduced into the housing 23, which chemically converts the water molecules enclosed during installation
Implementation Method 2
the medium absorbs water during hardening and chemically converts it
Implementation Method 3
the housing is hermetically sealed by welding, in particular laser welding, brazing with metal solder, soldering with glass solder or soft soldering
Implementation Method 4
If an electrical voltage is applied to the connections 5, this is transmitted in parallel to all the internal electrodes 7 and causes an electrical field in all layers of active material 2, which is thereby mechanically deformed
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to an actuator module (22) having a piezo-ceramic multi-layer actuator (1) which is arranged in a housing (23). So that increased conductivity, and therefore an increasing leakage current, does not occur at the actuator surface even after a long operating period, the invention proposes that the housing (23) be hermetically sealed and a space (24) which is partially filled or filled with a medium (21) which chemically converts and/or binds water be arranged between the multi-layer actuator (1) and the housing (23).