Electric Connection Box Provisional Mounting
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Solution Overview
Problem
Conventional electric connection boxes face difficulties in mounting efficiency due to large dimensional tolerances between bolt-fastening holes, leading to inaccuracies and increased time required for mounting on vehicle body panels.
Innovation Solution
The electric connection box features a provisionally-placing projection with a constricted engagement portion and separate screw passage holes, allowing for adjustable positioning and easy alignment, even with large dimensional tolerances, by forming a gap between the engagement portion and the mounting member's hole-defining surface, enabling screws to pass through easily.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If retaining pins are forcibly fitted into retaining holes using a bolt and nut, then the connection box body can be securely mounted on the bracket, but it becomes difficult to mount when the relative position accuracy between bolt-fastening through holes is low
Solution Approach 1:
The provisionally-placing projection is inserted into the provisionally-placing hole before the bolt-fastening operation. This preliminary positioning action establishes the correct relative position between the connection box body and bracket, ensuring that subsequent bolt insertion is straightforward even when hole position accuracy is low.
Solution Approach 2:
The provisionally-placing projection acts as an intermediary element between the connection box body and the bracket. It mediates the positioning process by providing a temporary but accurate reference position, which facilitates the subsequent permanent mounting operation using bolts and nuts.
2Reliability
If retaining pins are forcibly fitted into retaining holes, then secure engagement is achieved, but the mounting operation time increases due to alignment difficulties
Solution Approach 1:
By performing the provisional placement of the projection into the provisionally-placing hole before the final bolt-fastening operation, the time-consuming alignment process is separated from the securing process. This preliminary positioning is quick and easy, significantly reducing the overall mounting time while maintaining secure engagement through the subsequent bolt operation.
3Ease of manufacture
If large dimensional tolerances are used for bolt-fastening holes, then manufacturing cost is reduced, but mounting accuracy and ease of alignment deteriorate
Solution Approach 1:
The provisionally-placing projection provides a preliminary positioning function that compensates for large dimensional tolerances in the bolt-fastening holes. This allows the holes to be drilled with larger tolerances (reducing manufacturing cost) while still achieving accurate final positioning through the provisional placement step.
Solution Approach 2:
The mounting function is segmented into two distinct operations: provisional positioning (using the projection and provisionally-placing hole) and permanent fastening (using bolts and nuts). This segmentation allows each operation to be optimized independently - the provisional positioning handles alignment tolerance issues, while the permanent fastening provides secure attachment.
Data Source
AI summary
In an electric connection box, even if accuracy of a relative position between a first screw passage hole and a first screw hole, as well as accuracy of a relative position between a second screw passage hole and a second screw hole, is low, the relative positional relation between the first screw passage hole and the first screw hole, as well as the relative positional relation between the second screw passage hole and the second screw hole, can be adjusted because of the provision of a gap between an outer peripheral surface of a constricted engagement portion of a provisionally-placing projection and a hole-defining peripheral surface of a mounting member at the time of mounting a connection box body on the mounting member so that the passage of a first screw through the first screw passage hole and the first screw hole, as well as the passage of a second screw through the second screw passage hole and the second screw hole, can be easily carried out.