Electrical Junction Box Fastening Structure for PCB Looseness Under Vibration
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Solution Overview
Problem
Existing electrical junction boxes face issues with circuit board looseness due to wear of crush ribs under vibration, especially when weight increases, leading to ineffective suppression without using screws.
Innovation Solution
An electrical junction box design featuring a first case with a protruding portion that fits into a fitting hole of a second case through flexural deformation, and includes contact and non-contact portions to hold the circuit board securely without screws, utilizing flexural and curvature deformations of the second case to enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a crush rib is used to suppress circuit board looseness without screws, then device complexity is reduced, but reliability deteriorates under vibration and increased weight
Solution Approach 1:
The second side wall is designed to undergo flexural deformation dynamically during assembly to forcibly fit the protruding portion into the fitting hole, creating a secure mechanical interlock that adapts to dimensional variations while maintaining reliable attachment under vibration and weight loads
Solution Approach 2:
The second side wall is segmented into a fitting hole portion and a non-contact portion, allowing localized deformation at the fitting hole while maintaining structural integrity elsewhere, enabling reliable fastening without requiring complex screw mechanisms
2Strength
If the weight of the electrical junction box increases, then structural strength is improved, but the crush rib becomes easily worn due to vibrations
Solution Approach 1:
The fitting hole portion of the second side wall is designed to flex dynamically during assembly and operation, absorbing vibration energy through controlled deformation rather than rigid contact, preventing wear while maintaining structural strength in heavier configurations
Solution Approach 2:
The second side wall functions as a flexible structural element that undergoes controlled flexural deformation to achieve fitting, replacing the rigid crush rib mechanism with a more durable flexible fitting system that resists wear under vibration
3Ease of manufacture
If flexural deformation of the second side wall is used to fit the protruding portion, then manufacturing precision is reduced, but ease of manufacture is improved
Solution Approach 1:
The fitting hole portion is designed with controlled flexibility to undergo flexural deformation during assembly, accommodating dimensional variations and tolerances that would otherwise require high manufacturing precision, while still achieving reliable mechanical interlocking
Solution Approach 2:
The local flexibility parameter of the second side wall is modified in the fitting hole region, allowing controlled deformation that compensates for manufacturing tolerances and simplifies assembly while maintaining adequate fitting accuracy for functional requirements
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 suppresses circuit board looseness in both horizontal and vertical directions without screws, ensuring reliable attachment even under vibration, by using flexural and curvature deformations to maintain secure contact with the circuit board.
Implementation Method 1
a fitting hole into which the protruding portion is forcibly fitted by flexural deformation of the second side wall
Implementation Method 2
a claw body that is deformable in a curvature manner toward the second side wall side with respect to the first side wall, and the claw body allows the first contact portion to come into contact with the one surface of the circuit board by the curvature deformation, and is formed such that the claw body hooks onto the other surface of the circuit board by the curvature deformation being canceled
Data Source
AI summary
An electrical junction box includes a circuit board, a first case including a first side wall and covering one surface of the circuit board, a second case covering another surface of the circuit board opposite the one surface. The first case includes a first contact portion that comes into contact with the one surface of the circuit board, and the second case includes a pair of second contact portions that come into contact with the other surface of the circuit board at two positions interposing the fitting hole therebetween, and a non-contact portion that does not to come into contact with the other surface between the pair of second contact portions in order to allow the flexural deformation of the second side wall.