Thermally Expandable Junction Box for Switching Element Fire Protection
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Solution Overview
Problem
In electrical junction boxes, particularly in vehicles, there is a risk of switching elements overheating and catching fire due to malfunctioning fusible links or control elements, which existing protection mechanisms fail to address effectively.
Innovation Solution
Incorporating a thermally expandable expansion material member within the housing that separates from the circuit substrate at low temperatures but embeds the switching element when it overheats, preventing oxygen flow and potential fires, while also being designed to prevent short circuits when not overheated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fusible link and control element are used to protect the switching element, then the switching element is protected from overheating under normal conditions, but the protection fails in accidental situations where the fusible link does not blow out or the control element malfunctions
Solution Approach 1:
A thermally expandable material is introduced as an intermediary substance between the switching element and the surrounding environment. This material remains inactive at normal temperatures but activates at high temperatures by expanding to fill the housing space, physically isolating the switching element from oxygen and preventing fire even when primary protection mechanisms fail.
Solution Approach 2:
The thermally expandable material creates an inert atmosphere around the switching element when activated. By expanding to fill the housing and displacing oxygen, the material creates an oxygen-deprived environment that prevents combustion of the overheated switching element, effectively providing passive fire protection.
2Object-affected harmful factors
If the switching element is always surrounded by protective material, then fire protection is provided, but short circuits may occur due to material contact with the circuit substrate
Solution Approach 1:
The protective material transitions from a static to dynamic state based on temperature. At normal temperatures, the material remains in a compressed, low-volume state that prevents contact with electrical components. When overheating occurs, the material dynamically expands to fill the housing space, providing fire protection only when needed.
Solution Approach 2:
The volume and density of the protective material are changed based on temperature parameters. The thermally expandable material undergoes a parameter change from a compact state at low temperatures to an expanded state at high temperatures, allowing it to provide fire protection without causing short circuits under normal operating conditions.
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
Effectively prevents switching elements from catching fire by embedding them in a thermally expanded material, thereby isolating them from oxygen and preventing leakage of gases or particles, while ensuring no short circuits occur when not overheated.
Implementation Method 1
When a temperature of the switching element is high, the switching element is embedded in the thermally expanded expansion material member
Data Source
AI summary
Provided is an electrical junction box in which it is possible to prevent a switching element from catching fire. An electrical junction box according to one aspect of the present disclosure is an electrical junction box including: a circuit substrate on which a switching element is mounted on one side of the circuit substrate; and a housing member that houses the circuit substrate. The housing member further houses a thermally expandable expansion material member. When the temperature of the switching element is low, the expansion material member is spaced apart from the circuit substrate and the switching element, and is disposed at a position opposing the one side. When the temperature of the switching element is high, the switching element is embedded in the thermally expanded expansion material member.