Junction Box Cover Positioning via Geometric Interlock
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Solution Overview
Problem
Existing electrical junction boxes for motor vehicles face instability in holding the cover member in a standby position, leading to potential interference with adjacent components and increased complexity due to the use of spring members or backlash in rotary support axes.
Innovation Solution
The design incorporates an engaging projection on the casing and positioning wall portions on the cover member to securely hold the cover member in a first rotary end position, eliminating the need for additional biasing members and reducing backlash by integrating the guide projection and positioning wall portions with the casing and cover member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring member is used to hold the cover member in the first rotary end position, then the cover member can be held in the standby position, but the part count and structural complexity increase
Solution Approach 1:
The patent removes the spring member from the system entirely, extracting the biasing function and replacing it with a pure geometric solution using the engaging projection and positioning wall portions that provide passive mechanical positioning without additional active components
Solution Approach 2:
The engaging projection on the cover member automatically engages with the positioning wall portion on the casing through its own weight and geometry, making the system self-positioning without requiring external spring forces or additional actuation mechanisms
2Ease of operation
If the cover member is incorporated with the casing through rotary support axes, then the cover member can rotate to engage with the connector, but backlash and play in the axial direction cause unstable positioning
Solution Approach 1:
The engaging projection acts as an intermediary element between the cover member and casing, transferring and stabilizing the rotational position by engaging with the positioning wall portion to eliminate axial play while allowing rotational movement
Solution Approach 2:
The patent addresses the axial positioning problem by introducing a geometric constraint in the radial dimension through the engaging projection and positioning wall portion, converting the unstable axial positioning into a stable engagement through dimensional constraint
3Ease of operation
If the cover member is held apart from the connector-mounting section, then the connector can be attached and detached, but the cover member may interfere with adjacent electrical component-mounting sections
Solution Approach 1:
The engaging projection is pre-configured to engage with the positioning wall portion at the first rotary end position, preliminarily establishing the correct positioning of the cover member before any connector attachment or detachment operations occur, thereby preventing interference with adjacent components
Data Source
AI summary
An electrical junction box configured to stably hold a cover member in a standby state in a first position apart from a connector-mounting section. The electrical junction box includes a cover member rotatably attached to a casing about rotary support axes, an engaging projection provided on the casing that engages the cover member to position the cover member in the first position, a guide projection provided on one of the casing and the cover member, and a pair of positioning walls provided on the other of the casing and the cover member, wherein the cover member is positioned with respect to the engaging projection in an axial direction of the rotary support axes when the pair of positioning wall portions pinch the guide projection.