Piezoelectric Stack Insulation via Segmented Silicone Coating
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Solution Overview
Problem
Existing methods for producing piezoelectric bodies do not ensure reliable long-term operation due to potential electrical short circuits and inadequate mechanical and electrical insulation, particularly in high-stress applications like fluid injectors in the automotive sector.
Innovation Solution
A method involving spraying a silicone with an adhesion promoter to form an insulating layer on a stack of piezoelectric elements, followed by injection molding of additional silicone to create an encapsulating element, which embeds contact wires and provides mechanical and electrical insulation, while allowing for uniform layer formation and rapid crosslinking to prevent mechanical coupling loss under stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple silicone layers are applied manually with intermediate cleaning steps, then adhesion strength can be improved, but manufacturing complexity and production time increase
Solution Approach 1:
The silicone application process is segmented into two distinct stages: first spraying silicone with adhesion promoter to create a bonding layer, then injection molding additional silicone to form the final encapsulating element. This segmentation allows each step to be optimized independently while maintaining strong overall adhesion.
Solution Approach 2:
The adhesion promoter is applied in advance as a preliminary action before the main silicone application. This preliminary layer prepares the surface to ensure strong bonding occurs before the encapsulating silicone is molded, eliminating the need for intermediate cleaning steps.
2Reliability
If silicone is applied thickly to ensure complete insulation, then electrical insulation reliability improves, but manufacturing precision and layer uniformity deteriorate
Solution Approach 1:
The insulation structure is segmented into multiple layers: a thin adhesion promoter layer for bonding, an intermediate silicone layer for insulation, and an outer encapsulating layer for mechanical protection. This segmentation achieves complete insulation without requiring excessive thickness in any single layer.
Solution Approach 2:
Different regions of the silicone structure have different qualities optimized for their specific functions: the adhesion promoter layer provides bonding quality, the intermediate layer provides electrical insulation quality, and the outer layer provides mechanical protection quality.
3Strength
If adhesion promoter is always present in silicone, then bonding strength improves, but mechanical stability under shear stress deteriorates
Solution Approach 1:
The silicone structure is segmented into a bonding layer (with adhesion promoter) and an encapsulating layer (without adhesion promoter). This segmentation allows the bonding layer to provide strong adhesion while the encapsulating layer maintains mechanical stability under shear stress.
Solution Approach 2:
The adhesion promoter is locally present only in the bonding layer where strong adhesion is needed, while being absent from the encapsulating layer where mechanical stability and shear resistance are prioritized.
4Manufacturing precision
If manual cleaning of silicone from end faces is performed, then manufacturing precision improves, but productivity and automation capability deteriorate
Solution Approach 1:
The problematic step of manually cleaning silicone from end faces is completely extracted and eliminated from the manufacturing process. The method is designed so that no cleaning is needed, enabling full automation while maintaining precision.
Solution Approach 2:
The silicone application method is self-service in that it automatically produces clean surfaces without requiring post-processing. The adhesion promoter-based application ensures proper bonding without leaving excess silicone that would need removal.
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 method ensures strong adhesion and mechanical stability of the insulating and encapsulating layers, preventing electrical short circuits and enabling reliable operation of piezoelectric bodies over a long service life, even under high-stress conditions.
Implementation Method 1
a first silicone with an adhesion promoter is sprayed onto the stack of piezoelectric elements to form an insulating layer
Implementation Method 2
the stack of piezoelectric elements is heated with an adhesion promoter before the first silicone is applied to the stack of piezoelectric elements. This has the advantage that rapid crosslinking of the insulating layer is possible
Data Source
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AI summary
The invention relates to a method and to a device for producing a piezoelectric member (14), wherein the piezoelectric member (14) comprises a stack (16) of piezoelectric elements. In a first step, a first silicone comprising an adhesion promoter is sprayed onto the stack (16) of piezoelectric elements in order to create an insulation layer (24). Then, in another step another silicone is applied to the insulation layer (24) by way of injection molding in order to create an encasing element (22) that is adapted to encase at least a portion of the stack (16) of piezoelectric elements.