Segmented Ferromagnetic Layer for Wireless Charging
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Solution Overview
Problem
Ferromagnetic materials in handheld device housings cause heating issues and interference with wireless charging due to induced eddy currents, leading to potential damage and reduced charging efficiency when used in central locations.
Innovation Solution
A ferromagnetic accessory with a planar pattern of alternating ferromagnetic and nonferromagnetic material, where elongate members are spaced apart to minimize heat generation and allow for central magnetic mounting without interfering with inductive charging, enabling secure magnetic attachment and efficient wireless battery recharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a solid ferromagnetic material is used in the housing, then magnetic mounting capability is improved, but wireless charging efficiency deteriorates due to eddy current heating
Solution Approach 1:
The solid ferromagnetic material is segmented into a pattern of discrete ferromagnetic elements (dots, squares, or other geometric shapes) arranged in an array. This segmentation interrupts the continuous ferromagnetic paths that generate eddy currents during wireless charging, thereby reducing energy loss and heating while preserving sufficient magnetic flux for mounting capability.
Solution Approach 2:
The housing incorporates ferromagnetic material only in specific localized regions (the discrete elements) rather than uniformly throughout. This localized ferromagnetic property provides adequate magnetic mounting strength at the contact points with magnetic mounts while allowing electromagnetic fields to pass through non-ferromagnetic regions during wireless charging, minimizing eddy current effects.
2Stability of the object's composition
If ferromagnetic material is placed in a central location, then magnetic mounting stability is improved, but wireless charging capability deteriorates due to interference with inductive coils
Solution Approach 1:
The central ferromagnetic region is segmented into multiple discrete elements distributed across the housing surface. This segmentation allows the magnetic mounting function to remain effective at the center (providing stability) while the gaps between segmented elements permit electromagnetic field penetration for wireless charging, reducing interference with inductive coils.
Solution Approach 2:
The ferromagnetic elements are designed with specific geometric shapes and size distributions that optimize magnetic mounting performance in the central region while minimizing impact on wireless charging. The asymmetric arrangement and varying sizes of elements create magnetic flux paths that support stable mounting without forming continuous eddy current loops that would interfere with charging.
3Loss of energy
If ferromagnetic material is removed from the housing, then wireless charging efficiency is improved, but magnetic mounting capability deteriorates
Solution Approach 1:
Instead of completely removing ferromagnetic material, the housing retains segmented ferromagnetic elements that are sufficient for magnetic mounting. The segmentation reduces the total ferromagnetic cross-section to levels that minimize eddy current heating during wireless charging while maintaining adequate magnetic flux density for secure mounting capability.
Solution Approach 2:
The ferromagnetic material parameters (such as element size, spacing, shape, and distribution density) are optimized to achieve a balance between magnetic mounting strength and wireless charging efficiency. By adjusting these parameters, the housing maintains sufficient magnetic properties for mounting while reducing ferromagnetic content to levels that minimize interference with inductive charging fields.
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
The solution provides a damage-resistant, centrally mountable ferromagnetic housing that maintains wireless charging efficiency and stability, supporting the weight of handheld devices while preventing excessive heating and ensuring secure magnetic coupling.
Implementation Method 1
a ferromagnetic layer coupled to the housing and forming a planar pattern of alternating areas defined by ferromagnetic material and nonferromagnetic material
Implementation Method 2
the electromagnetic field likely induces eddy currents in the ferromagnetic disc, which due to resistance, thereby creates heat
Implementation Method 3
a fluctuating electromagnetic field created by the inductive coil of the wireless charging unit. This is likely caused by the ferromagnetic material heating up due to a fluctuating electromagnetic field
Data Source
AI summary
A ferromagnetic accessory for a handheld device is disclosed. Embodiments include a housing having a first side and a second side, the first side adapted to be coupled to and cover at least a portion of a handheld device, and a ferromagnetic layer coupled to the housing and forming a planar pattern of alternating areas defined by ferromagnetic material and nonferromagnetic material. In at least one embodiment, the ferromagnetic material comprises elongate members and the ferromagnetic layer comprises a plurality of spaced-apart elongate members defining nonferromagnetic material areas therebetween. In other embodiments, the ferromagnetic layer is embedded within the housing. In other embodiments, the ferromagnetic accessory is a contiguous layer, a composite of an elastomer and ferromagnetic material and can be coupled directly to a handheld device or to the outside of a housing.