Waterproof Fan Cover Structure for Thermal Stress Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing waterproof fans face issues with thermal stress due to differences in the coefficient of linear expansion between metal or resin waterproof covers and epoxy resin, leading to separation and reduced water resistance.
Innovation Solution
A waterproof fan design featuring a waterproof cover with a partitioning portion and protruding portions that fill gaps between windings and stator cores with a second resin, enhancing bond strength and reducing thermal stress, while minimizing resin usage for improved production efficiency and weight reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal or resin waterproof cover is used to cover the circuit board, then water resistance is improved, but thermal stress causes separation between the cover and epoxy resin due to differences in the coefficient of linear expansion
Solution Approach 1:
The waterproof cover is segmented into a cover body and separate protruding portions that extend into gaps between windings. This segmentation allows the protruding portions to independently fill gaps and bond with resin, while the cover body maintains water resistance, thus resolving the thermal stress separation issue while preserving bond strength.
Solution Approach 2:
The protruding portions act as intermediaries between the waterproof cover and the epoxy resin. By extending into the gaps between windings, they provide a transition zone that accommodates differential thermal expansion, preventing direct stress concentration at the cover-resin interface and maintaining bond strength under thermal stress.
2Reliability
If epoxy resin is used to fill spaces around the circuit board and windings, then water resistance is improved, but the amount of resin required increases
Solution Approach 1:
The protruding portions extract the function of gap-filling from the bulk epoxy resin. By providing structural elements that extend into the gaps between windings, they reduce the volume of resin needed to achieve the same water resistance, thus decreasing the quantity of substance while maintaining reliability.
Solution Approach 2:
The protruding portions provide localized water resistance at critical gap regions between windings, rather than requiring uniform resin coverage throughout. This local quality approach concentrates resin usage where it is most needed, reducing the overall amount of resin while maintaining effective water resistance.
3Reliability
If a waterproof cover is used to separate the circuit board from windings, then water resistance is improved, but the bond strength between the cover and resin decreases due to thermal stress
Solution Approach 1:
The waterproof cover is divided into a main cover body and separate protruding portions. This segmentation allows the protruding portions to serve as dedicated bonding elements that extend into gap regions, providing multiple bond interfaces between the cover and resin, thereby maintaining bond strength despite thermal stress on the main cover body.
Solution Approach 2:
The protruding portions extend the cover structure into the radial dimension by reaching into gaps between windings. This dimensional extension creates additional bonding surfaces and distribution of thermal stress across multiple interfaces, preventing single-point failure and maintaining overall bond strength under thermal cycling.
Data Source
AI summary
A waterproof fan includes: a rotating blade configured to be rotatable about a rotation axis; a rotor including a permanent magnet; a stator including a plurality of stator cores located on an inner diameter side relative to the rotating blade, the plurality of stator cores extending in a radial direction relative to the rotation axis, and windings each wound around a respective stator core; a circuit board electrically connected to the windings; a waterproof cover including a first resin, the waterproof cover covering the circuit board; and a molded portion including a second resin, the molded portion covering at least the stator, the waterproof cover includes: a partitioning portion separating the windings from the circuit board; and a protruding portion protruding from the partitioning portion into a space between the windings, and gaps between the windings, and the partitioning portion and the protruding portion are filled with the second resin.