Wireless Power Inductor Case Design for Stress Mitigation
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Solution Overview
Problem
Conventional inductors for wireless power transmission face issues with mechanical stress and heat dissipation, leading to reduced inductance values and increased core losses due to resin curing shrinkage and thermal stress on magnetic cores.
Innovation Solution
The design incorporates a case made of insulating material to house the magnetic core, with a stress-absorbing member and a resin that covers the case and winding, preventing direct contact and stress application, while using a stress-absorbing member to mitigate thermal and curing shrinkage effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the resin is cast to cover the magnetic core and winding, then mechanical strength and heat dissipation are improved, but stress is applied to the magnetic core due to curing shrinkage, causing reduction in inductance value or increase in core loss
Solution Approach 1:
A case made of insulating material is introduced as an intermediary component between the magnetic core and the resin. The case houses the magnetic core and prevents direct contact with the resin, thereby eliminating the stress transmission path from the resin to the magnetic core while still allowing the resin to provide mechanical strength and heat dissipation functions
2Reliability
If a stress-absorbing member is added to cover the magnetic core, then stress is suppressed, but the device complexity increases
Solution Approach 1:
The case combines multiple functions into a single component: it provides mechanical support for the magnetic core, acts as a stress-absorbing barrier against resin shrinkage, offers electrical insulation, and facilitates heat dissipation. This merging eliminates the need for separate stress-absorbing members while achieving the same protective effect
3Stress or pressure
If the case is made larger to accommodate the magnetic core with clearance, then stress from resin is reduced, but the volume of the inductor increases
Solution Approach 1:
The case is designed as a thin-walled insulating structure that provides sufficient clearance between the magnetic core and the resin without adding significant volume. The thin film-like case effectively transmits stress while maintaining compact inductor dimensions
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 configuration effectively suppresses stress on the magnetic core, improving mechanical strength and heat radiation performance, thereby reducing inductance value degradation and core losses.
Implementation Method 1
stress has been applied to the magnetic core due to curing shrinkage of the resin occurred when performing the casting
Implementation Method 2
When the stress is applied to the magnetic core, a magnetostriction of the magnetic core is impeded
Implementation Method 3
using a stress-absorbing member to mitigate thermal and curing shrinkage effects
Data Source
AI summary
An inductor according to one embodiment includes a magnetic core, a case, a winding, and a resin. The case is configured to house the magnetic core. The winding is configured to be wound around the case. The resin is configured to be formed of a first resin to cover the case and the winding. A difference between an inside dimension of the case and a dimension of the magnetic core in the same direction is greater than a variation of a dimension of the case in the direction when forming the resin.