Electric Junction Box Connector Fitting Segmentation
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Solution Overview
Problem
Conventional electric junction boxes for automobiles are costly due to the use of expensive heat-resistant resin for the connector fitting portion and the need for screws for fixation, which increases production costs.
Innovation Solution
The connector fitting portion is designed with a holding portion made of heat-resistant resin and an outer wall made of non-heat-resistant resin, where the holding portion is attached to the case using press-fitting and bonding, eliminating the need for screws and reducing the amount of heat-resistant resin required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the connector fitting portion is made entirely of heat-resistant resin to withstand soldering heat, then the resin can resist the heat of reflow soldering or flow soldering, but the cost increases significantly due to the expensive heat-resistant resin material
Solution Approach 1:
The connector fitting portion is divided into two distinct parts: a holding portion made of heat-resistant resin that withstands soldering heat, and an outer wall made of non-heat-resistant resin that provides structural support. This segmentation allows each part to be optimized for its specific function, using expensive heat-resistant material only where absolutely necessary (holding portion) rather than throughout the entire connector fitting portion.
Solution Approach 2:
Different material properties are applied to different regions of the connector fitting portion. The holding portion uses heat-resistant resin with high temperature resistance for localized heat exposure during soldering, while the outer wall uses standard non-heat-resistant resin for structural purposes. This local differentiation of material quality reduces overall material cost while maintaining functional reliability.
2Reliability
If screws are used to fix the connector fitting portion to the case, then the connection is secure and reliable, but the cost increases due to additional screw components and assembly steps
Solution Approach 1:
The connector fitting portion is integrated directly with the case through press-fitting, merging two separate components (connector fitting portion and case) into a unified assembly. This eliminates the need for separate fastening elements like screws, reducing component count and assembly complexity while maintaining secure connection through the press-fitted interface.
Solution Approach 2:
The mechanical screw fastening system is replaced with a press-fitting mechanism. Instead of using threaded fasteners requiring holes and tightening operations, the design uses interference fitting where the connector fitting portion is pressed into the case, creating a secure mechanical bond through friction and geometric interlocking without additional fasteners.
3Temperature
If the entire connector fitting portion is made of heat-resistant resin, then heat resistance is ensured, but the production cost increases due to material expense
Solution Approach 1:
The connector fitting portion is segmented into a holding portion requiring heat resistance and an outer wall not requiring heat resistance, allowing differential material selection that optimizes both performance and cost.
Solution Approach 2:
Heat-resistant material properties are applied locally only to the holding portion where thermal exposure occurs during soldering, rather than uniformly across the entire connector fitting portion. This localized application of heat resistance reduces material cost while maintaining functional integrity.
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 reduces production costs by minimizing the use of expensive heat-resistant resin and eliminates the need for screws, while ensuring accurate positioning and preventing deformation of the connector fitting portion, thus enhancing the assembly process and reducing the risk of external force application on the soldered portions.
Implementation Method 1
the holding portion is made of heat-resistant resin which is resistant to heat used during the soldering
Implementation Method 2
the outer wall is made of non-heat-resistant resin which melts due to the heat used during the soldering
Implementation Method 3
the holding portion is attached to the case by press-fitting the projection into the recessed portion or into the through hole
Implementation Method 4
by inserting the projection into the recessed portion or into the through hole followed by bonding the projection to the recessed portion or to the through hole
Data Source
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AI summary
There is provided an electric junction box (1) which can reduce the usage of the heat-resistant resin for a connector fitting portion. The electrical junction box (1) includes a case (4) including a box-like body (3) and a box-like body (2) to be assembled together, a substrate (5) received in the case (4), a connector fitting portion (9) arranged to engage with a connector and having a terminal (6) soldered to the substrate (5) with lead-free solder, a holding portion (19) holding the terminal (6), and a tubular outer wall (8) surrounding the terminal (6). The holding portion (19) and the outer wall (8) are formed as separate parts. The outer wall (8) is divided into two segments formed integrally with the box-like bodies (3, 2), respectively. The holding portion (9) is made of heat-resistant resin while the outer wall (8) is made of non-heat-resistant resin.