Radio Controlled Timepiece Antenna Eddy Current Isolation
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Solution Overview
Problem
Radio controlled timepieces with metal housings face reduced reception sensitivity due to eddy currents caused by magnetic flux from metal members near the antenna structure, which affects the antenna's ability to receive radio waves effectively.
Innovation Solution
The design includes a metal back cover and case with specific fixing structures that prevent eddy currents by ensuring no direct contact with the antenna, using insulating materials and strategically placing fixing elements to minimize the flow of alternating magnetic flux, thereby maintaining high reception sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a metal housing is used for the timepiece, then design quality and aesthetics are improved, but reception sensitivity of the antenna is reduced due to eddy currents
Solution Approach 1:
A non-conductive adhesive is introduced as an intermediary substance between the metal antenna structure and the metal housing. This adhesive layer prevents direct contact between the metal components, thereby blocking the formation of eddy current paths while still providing mechanical bonding. The adhesive acts as a mediator that allows the metal housing to maintain its structural and aesthetic functions without compromising antenna reception sensitivity.
2Strength
If metal members are placed near the antenna structure, then housing strength and design flexibility are improved, but eddy current losses increase and reduce reception sensitivity
Solution Approach 1:
The non-conductive adhesive serves as a mediator that allows metal members to be positioned near the antenna structure for structural support and design flexibility, while simultaneously preventing the formation of eddy current paths by electrically isolating the metal components from each other.
Solution Approach 2:
The housing is divided into multiple metal components (case, back cover, etc.) that are joined using non-conductive adhesives. This segmentation breaks up continuous metal paths that would otherwise allow eddy currents to flow, while still maintaining the overall structural strength through the distributed adhesive bonding.
3Ease of manufacture
If the back cover is directly fixed to the case with metal fixing structures, then assembly is simplified and manufacturing cost is reduced, but eddy currents are generated and reception sensitivity is reduced
Solution Approach 1:
A non-conductive adhesive is used as a fixing structure between the back cover and the case, replacing traditional metal fixing methods. This adhesive mediator maintains the simplicity of assembly (no screws or clips needed) while simultaneously preventing eddy current formation by providing electrical isolation between the metal components.
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 enhances the reception sensitivity of the radio controlled timepiece by preventing eddy current losses and ensuring stable fixation of the back cover to the case, even when made of metal, while simplifying assembly and reducing production costs.
Implementation Method 1
magnetic flux produced in the antenna structure due to received radio waves
Implementation Method 2
magnetic flux produced in the antenna structure due to received radio waves passes these metal members, thereby producing eddy currents, which brings about an eddy current loss
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A radio controlled timepiece comprising a housing (10) and an antenna structure (8) encased within the housing. The antenna structure includes a bar shaped core (81) and a coil (82) wound around the core for receiving radio waves to set a current time. The housing comprises a short hollow cylindrical metal case (1) and a metal back cover (6) engaged with one end of the case for closing purpose. The housing further comprises a housing fixing structure (15) provided only on one of two parts of the housing divided by an axis of the bar shaped core.