Junction Box Dividing Wall Height for Submersion Fire Prevention

Solution Overview

Problem

Conventional electrical junction boxes fail to prevent vehicle fires caused by water intrusion during submersion events like tsunamis or floods, as they cannot effectively isolate high-voltage and low-voltage circuit regions, leading to potential short circuits and electrolysis after water recedes.

Innovation Solution

An electrical junction box design featuring a lower case with a protruding peripheral wall, a high-voltage circuit region, a low-voltage circuit region, and a dividing wall that separates these regions, with the dividing wall's height exceeding the peripheral wall's height, ensuring electrical insulation and providing drain holes to facilitate water drainage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional waterproof structures with sealing members are used to prevent water intrusion during normal use, then waterproofing performance is improved, but the ability to prevent vehicle fires after submersion deteriorates because water accumulates inside the junction box

Engineering Contradiction:

Improvewaterproofing performanceVSAvoidvehicle fire risk after submersion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The junction box is divided into multiple isolated compartments using partition walls. Each compartment contains specific circuit components and is separated from others, preventing water from creating continuous conductive paths between different circuits. This segmentation maintains waterproofing while preventing post-submersion short circuits and fires.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the junction box are designed with different structural characteristics. The partition walls create localized dry zones and controlled water drainage paths. Sealing members are strategically placed at specific locations rather than uniformly throughout, providing targeted waterproofing while allowing controlled water management in critical areas.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If the junction box is sealed to prevent water entry during normal operation, then protection against water splashes is improved, but the ability to drain accumulated water after submersion deteriorates

Engineering Contradiction:

Improveprotection against water splashesVSAvoidwater drainage capability

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

Drainage holes are pre-designed and positioned at the lowest points of each compartment during the manufacturing stage. These holes are initially blocked by sealing members to prevent water entry during normal use, but automatically open to drain water when the junction box is submerged and water pressure exceeds the sealing force, enabling automatic water removal without additional components.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Sealing members serve as intermediary elements that can dynamically switch between blocking and allowing water passage. These members are positioned at drainage holes and automatically respond to water pressure changes, providing waterproofing during normal operation while enabling drainage after submersion without requiring active control systems.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If high-voltage and low-voltage circuits are housed in the same junction box to simplify the electrical system, then device complexity is reduced, but the risk of short circuits between circuits deteriorates when water intrudes

Engineering Contradiction:

Improveelectrical system integrationVSAvoidelectrical insulation between circuits

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The junction box is divided into multiple isolated compartments using partition walls. Each compartment contains specific circuit components and is separated from others, preventing water from creating continuous conductive paths between different circuits. This segmentation maintains waterproofing while preventing post-submersion short circuits and fires.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the junction box are designed with different structural characteristics. The partition walls create localized dry zones and controlled water drainage paths. Sealing members are strategically placed at specific locations rather than uniformly throughout, providing targeted waterproofing while allowing controlled water management in critical areas.

Inventive Principle:

Principle #3Local quality

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 design effectively prevents short circuits and electrolysis between high-voltage and low-voltage circuit regions by maintaining electrical insulation after water recedes, reducing the risk of vehicle fires by ensuring complete isolation and facilitating water drainage.

Implementation Method 1

the height dimension of the dividing wall from the bottom wall is configured to be greater than a height dimension of the peripheral wall from the bottom wall... bodies of water containing electrolytes such as those in salt water remaining in the high-voltage circuit region and the low-voltage circuit region inside the peripheral wall are kept apart by the dividing wall after water has receded... prevent the intrusion of water due to a tsunami, a flood, or the like

Methodology Applied

Scientific EffectElectrical insulation: Electrical Resistance

Implementation Method 2

the lower case includes a bottom wall and a peripheral wall provided so as to protrude from a peripheral edge portion of the bottom wall toward the upper case... a high-voltage circuit region in which the high-voltage circuit bus bar is disposed, a low-voltage circuit region in which the low-voltage circuit bus bar is disposed, and a dividing wall that divides the high-voltage circuit region and the low-voltage circuit region

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Data Source

PatentUS9981618B2Electrical junction box

Publication Date: 2018.05.29 SUMITOMO WIRING SYSTEMS LTD

AI summary

Provided is an electrical junction box configured promptly release the electrical junction box from a state where water has intruded therein, thereby preventing the occurrence of a vehicle fire due to submersion. An internal circuit includes a high-voltage circuit bus bar and a low-voltage circuit bus bar having a lower potential than the high-voltage circuit bus bar, and a lower case includes a bottom wall and a peripheral wall protruding from a peripheral edge portion of the bottom wall toward an upper case. A high-voltage circuit region where the high-voltage circuit bus bar is disposed, a low-voltage circuit region where the low-voltage circuit bus bar is disposed, and a dividing wall divides these regions are provided inside the peripheral wall, and a height dimension of the dividing wall from the bottom wall is configured to be greater than a height dimension of the peripheral wall from the bottom wall.