Sealed Automotive Fuse Box Busbar Injection Molding
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Solution Overview
Problem
Fuses in extreme environments face challenges from dust and moisture ingress, which can damage the electrical fuse box and compromise protection.
Innovation Solution
A dust- and moisture-resistant fuse assembly is manufactured using an injection molded base, where busbars are coated with a sealant and embedded in plastic during the injection molding process, forming a bonded material that prevents moisture and dust ingress, achieving an IP67-compliant rating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional fuse box structure is used, then the manufacturing process is simple, but dust and moisture can enter the fuse box causing damage
Solution Approach 1:
The patent combines the sealing function with the manufacturing process by integrating sealant application and plastic injection molding into a single operation. The sealant is applied to the busbar, and then plastic is injected to simultaneously form the enclosure and create the seal, merging two functions (sealing and enclosure formation) into one integrated process step.
Solution Approach 2:
The patent uses composite materials by combining metal busbar with plastic enclosure through a bonded interface. The sealant creates a composite structure where metal and plastic are permanently bonded, forming a unified assembly that provides both structural support and environmental protection.
2Reliability
If the busbar is coated with sealant and embedded in plastic, then dust and moisture ingress is prevented, but the manufacturing process becomes more complex
Solution Approach 1:
The sealant is applied to the busbar before the plastic injection molding process. This preliminary sealing action ensures that the bonding interface is prepared in advance, allowing the plastic to bond to the sealant-coated busbar during injection, thereby preventing dust and moisture ingress from the outset.
Solution Approach 2:
The sealant acts as an intermediary material between the metal busbar and the plastic enclosure. It facilitates bonding between these two dissimilar materials, creating a permanent seal that prevents environmental contaminants from penetrating the interface between metal and plastic components.
3Strength
If melted plastic is injected at high pressure, then the bond between sealant and plastic is irreversible, but the manufacturing equipment requirements increase
Solution Approach 1:
The patent utilizes parameter changes by controlling the temperature and pressure of the injected plastic. The plastic is heated to a molten state for injection, then cooled within the mold to solidify and form a strong permanent bond with the sealant-coated busbar. These parameter changes (temperature and pressure) enable the creation of an irreversible bond.
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 prevents damage from dust and moisture, ensuring reliable overcurrent protection in extreme environments by creating a tight, irreversible bond between metal busbars and plastic, enhancing the durability and reliability of the fuse assembly.
Implementation Method 1
baking the busbar in an oven until the sealant is cured onto the busbar
Implementation Method 2
the melted plastic and the sealant form a bonded material that cannot be subsequently separated by heating
Data Source
AI summary
A fuse assembly including a fuse connected to two busbars, an injection molded base and an injection molded cover. The busbars are powder-coating with a powder-based adhesive or adhesion promoter, then cured in an oven. The busbars are then placed in the cavity image of an injection molding apparatus. Plastic is heated to a liquid form and injected into the cavity image. The resulting injection molded base is resistant to both dust and water, protecting the fuse inside.