Electric Junction Box Cooling Layout for Relay Joule Heat

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Solution Overview

Problem

Existing electric junction boxes struggle with inefficient heat dissipation, particularly from electronic components like relays and fuses, leading to potential operational issues due to Joule heat generation.

Innovation Solution

The electric junction box design incorporates a cooling member sandwiched between a pair of conductive members, with each member's mounting wall facing the cooling member's outer surface, allowing for efficient heat absorption and dissipation, and includes a heat transfer paste to enhance heat transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electronic components are disposed inside a housing portion with busbar on mounting wall, then electrical connection is achieved, but Joule heat generation occurs in internal circuit and contact points

Engineering Contradiction:

Improveelectronic component operationVSAvoidJoule heat

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

A cooling member is introduced as an intermediary between the mounting wall and the external environment. This cooling member includes a heat absorption portion that contacts the mounting wall to absorb Joule heat, and a heat dissipation portion that extends toward the external environment to dissipate the absorbed heat, thereby mediating the heat transfer process and protecting electronic components from excessive heat generation

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If cooling member is used for heat dissipation, then heat can be absorbed and dissipated, but the cooling member size increases

Engineering Contradiction:

Improveheat dissipation efficiencyVSAvoidcooling member size

Core Design Contradiction:

TemperatureVSVolume of moving object

Solution Approach 1:

The cooling member utilizes the thickness direction of the mounting wall as a new dimension for heat dissipation. The heat absorption portion is disposed inside the housing portion contacting the mounting wall in this thickness direction, while the heat dissipation portion extends toward the external environment along the same direction. This dimensional approach allows efficient heat dissipation without significantly increasing the overall size of the cooling member

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Temperature

If conductive members are disposed to sandwich cooling member, then heat absorption capability is maximized, but device complexity increases

Engineering Contradiction:

Improveheat absorption capabilityVSAvoidstructural complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The mounting wall serves multiple functions: it provides electrical connection through the busbar, supports electronic components, and acts as a heat transfer interface to the cooling member. By making the mounting wall multi-functional, the patent avoids adding separate structures for each function, thereby reducing overall device complexity while still achieving effective heat absorption through the sandwiched cooling member configuration

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 configuration enables effective heat dissipation, reduces the cooling member's size, facilitates miniaturization, and maintains stable operation by preventing components from interfering with each other, while ensuring long-term heat dissipation efficiency.

Implementation Method 1

a cooling member capable of absorbing heat from outer surfaces and dissipating heat to the outside

Methodology Applied

Scientific EffectHeat absorption: Absorption (physical)

Implementation Method 2

a cooling member capable of absorbing heat from outer surfaces and dissipating heat to the outside

Methodology Applied

Scientific EffectHeat dissipation: Thermal Radiation

Implementation Method 3

includes a heat transfer paste to enhance heat transfer

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 4

Joule heat associated with energization is generated in an internal circuit of the electronic component

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS12580369B2Electric junction box

Publication Date: 2026.03.17 YAZAKI CORP

AI summary

An electric junction box includes: a cooling member; and a pair of conductive members disposed to sandwich the cooling member. Each of the pair of conductive members includes a housing portion, an electronic component disposed inside the housing portion, and a busbar that is provided on a mounting wall as one box wall of the housing portion and is electrically connected to the electronic component, and each of the pair of conductive members is disposed such that an outer surface of the mounting wall faces the outer surface of the cooling member. The electronic component includes a plurality of terminals, and a movable contact point that is provided inside the electronic component, and the electronic component is configured in such a manner that the movable contact point is located at a position farther away from the side wall than the plurality of terminals in the electronic component.