Electrical Sheet Composite Bonding With Selective Adhesive Activation
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Solution Overview
Problem
Existing methods for producing composite electrical sheets using adhesive layers fail to maintain adhesive strength at elevated temperatures, leading to instability in rotor or stator applications where temperatures exceed 125°C, and partial activation of adhesive layers during heating processes disrupt subsequent processes.
Innovation Solution
A method involving thermally activated polymer-based adhesive layers, where only the sides of electrical sheets facing each other are activated before contact, ensuring the outward-facing adhesive layers remain inactive, and multiple sheets are connected under force, with optional additional connection methods like welding or clinching, using a preferred composition of epoxy resin, latent hardener, and accelerator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the entire surface of coated electrical steel strips is heated to activate the adhesive layer, then bonding strength is improved, but the outward-facing adhesive layers become activated which disrupts subsequent processes
Solution Approach 1:
The patent applies local quality by heating only the specific regions where adhesive activation is needed (at the bonding interfaces between sheets) while leaving the outward-facing adhesive layers unheated and inactive. This selective localized heating resolves the contradiction by achieving bonding strength where required without causing unwanted activation elsewhere.
Solution Approach 2:
The heating process is segmented into distinct zones: heated zones at the bonding interfaces and unheated zones at the outward-facing surfaces. This segmentation allows different parts of the composite structure to have different thermal states, enabling adhesive activation only where needed while preserving the functionality of outward-facing adhesives for subsequent processes.
2Ease of manufacture
If standard adhesive layers are used for bonding electrical sheets, then ease of manufacture is improved, but adhesive strength is lost at elevated temperatures above 125°C
Solution Approach 1:
The patent changes the thermal parameter threshold of the adhesive by selecting high-temperature resistant adhesive materials that maintain their bonding properties above 125°C. This parameter change allows the adhesive to withstand the elevated temperatures in rotor/stator applications while retaining sufficient bonding strength, resolving the contradiction between ease of manufacture and high-temperature 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
This approach maintains adhesive strength at elevated temperatures, prevents unwanted activation of adhesive layers, and allows for efficient production of composite electrical sheets suitable for high-temperature applications, enhancing the stability and efficiency of the punching process.
Implementation Method 1
the adhesive layer is thermally activated before contacting only on the side of the first electrical sheet and/or at least second electrical sheet that faces the contacting and connection with another electrical sheet
Implementation Method 2
an adhesive layer in the present invention is understood to be an adhesive which shows little loss in adhesion even at elevated temperatures (>125 °C), i.e. tensile shear strengths > 3.5 N/mm²
Implementation Method 3
the electrical sheets are brought into contact with one another and are bonded together to form a composite under the influence of force
Data Source
Figure 1
AI summary
The present invention relates to a method for producing a composite (V) of electrical steel sheets, in which a first electrical steel sheet (1), which is coated on both sides with a thermally activatable polymer-based adhesive layer, and at least one second electrical steel sheet (1), which is coated on both sides with a polymer-based plastic layer, are provided, wherein the electrical steel sheets (1) are brought into contact with one another and are joined together to form a composite (V) under the influence of force, wherein, prior to being brought into contact, the adhesive layer is thermally activated only on the side of the first electrical steel sheet (1) which faces the second electrical steel sheet (1).