Co-based Amorphous Antenna Core for Low-Frequency Communication
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Solution Overview
Problem
Existing antenna cores for keyless entry systems, particularly those using ferrite or Fe-based amorphous metal thin strips, face issues with fragility, low impact resistance, magnetic flux saturation, and corrosion, leading to poor manufacturing yields and inadequate communication properties in low-frequency bands.
Innovation Solution
A Co-based amorphous magnetic alloy thin strip laminate with a length-to-short-axis ratio greater than 1, featuring line-shaped marks along the long axis, is used to create an antenna core with improved magnetic properties and resistance to corrosion, allowing for enhanced communication in low-frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amorphous metal thin strips are heat-treated to exhibit desired magnetic property, then magnetic property is improved, but the thin strips become extremely fragile and manufacturing yield deteriorates
Solution Approach 1:
The patent changes the heat treatment parameters by conducting treatment at lower temperatures (50-150°C) for extended periods (1 hour to several days) instead of conventional high-temperature short-time treatment. This parameter modification allows achieving desired magnetic properties while preventing the thin strips from becoming excessively fragile, thereby improving manufacturing yield.
Solution Approach 2:
The patent creates a composite structure by stacking multiple amorphous metal thin strips with insulating resin layers between them. This composite construction provides mechanical support and reduces fragility of individual strips while maintaining the desired magnetic properties of the amorphous metal material.
2Reliability
If thickness of laminate of stacked amorphous metal thin strips is increased to avoid magnetic flux saturation, then magnetic flux density is improved, but space factor increases and size reduction becomes difficult
Solution Approach 1:
The patent changes the material parameters by using Co-based amorphous metal thin strips with superior magnetic properties compared to conventional Fe-based strips. These strips achieve higher magnetic flux density with lower thickness, enabling compact antenna core design without magnetic flux saturation.
Solution Approach 2:
The patent optimizes the local magnetic properties by carefully selecting and stacking Co-based amorphous metal thin strips with specific characteristics in different positions within the laminate, achieving uniform magnetic flux distribution and preventing saturation while minimizing overall thickness.
3Quantity of substance
If Fe-based amorphous metal thin strips are used to reduce cost, then manufacturing cost is reduced, but corrosion resistance deteriorates
Solution Approach 1:
The patent uses Co-based amorphous metal thin strips which inherently possess better corrosion resistance than Fe-based strips. The material selection at the composite level provides both the required magnetic properties and improved corrosion resistance without requiring additional protective coatings.
Solution Approach 2:
The patent employs a design where the amorphous metal thin strips are stacked with insulating resin layers that provide corrosion protection. This approach replaces the need for expensive corrosion-resistant coatings on Fe-based strips while maintaining cost-effectiveness through the use of standard amorphous metal materials.
4Reliability
If number of stacked amorphous metal thin strips is increased to improve magnetic flux density, then magnetic property is improved, but space factor decreases and thickness increases
Solution Approach 1:
The patent changes the quality parameters of the amorphous metal thin strips by using Co-based material with higher intrinsic magnetic flux density. This allows achieving the required magnetic flux density with fewer strips and reduced total thickness compared to using conventional Fe-based strips.
Solution Approach 2:
The patent extracts and eliminates the need for excessive stacking of thin strips by using material with superior magnetic properties. The improved material characteristics reduce the number of strips required, thereby decreasing the overall antenna core thickness while maintaining adequate magnetic flux density.
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 Co-based amorphous magnetic alloy antenna core achieves improved magnetic flux density, corrosion resistance, and communication properties in the 120 to 130 kHz frequency band, reducing size and thickness while maintaining robustness and reliability.
Implementation Method 1
the amorphous metal thin strips are first heat-treated in an air atmosphere at 550° C. for one hour
Implementation Method 2
with the use of epoxy resin, two-hour heating at 120° C. is conducted for curing or with the use of a urethane potting material, two-hour heating at 80° C. is conducted for curing
Implementation Method 3
a door handle of an automobile having a built-in antenna, and as its antenna core, a ferrite core is used. Though low-priced, the ferrite core has a problem of being easily broken due to its low impact resistance
Data Source
AI summary
An antenna core includes a laminate of a plurality of Co-based amorphous magnetic alloy thin strips in which a length ratio of a long axis to a short axis is greater than 1. 60% or more of the Co-based amorphous magnetic alloy thin strips in terms of the number of the thin strips as percentage have a line-shaped mark formed along the long axis on at least one surface thereof. An antenna includes the antenna core and a winding wound around the antenna core along the long axis.