Antenna Unit With Protruding Sensor Coil For Keyless Entry
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing antenna units in electronic key systems face issues with eddy-current loss affecting signal transmission and reception, and incorrect door unlocking due to sensor electrode placement, which can lead to malfunctions when the user touches the outer side of the door handle.
Innovation Solution
An antenna unit design featuring an antenna coil wound on a bobbin with a protruding electrode coil winding part allows for precise detection of capacitance changes in one direction, preventing malfunctions by ensuring the sensor electrode is wound in a specific direction to detect intended state changes and avoiding eddy-current losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If one of the core sheets constituting the core is used as the sensor electrode, then the door unlocking function is achieved, but eddy current is generated in the sensor electrode when the antenna coil is energized, causing eddy-current loss that affects signal transmission and reception
Solution Approach 1:
The sensor electrode is extracted from the core structure and placed on a separate bobbin. This separation removes the sensor electrode from the magnetic flux path of the antenna coil, eliminating eddy current generation while preserving the capacitance detection function for door unlocking.
Solution Approach 2:
A non-magnetic bobbin structure is introduced as an intermediary carrier for the sensor electrode. This mediator allows the sensor electrode to be positioned independently from the core, enabling capacitance detection without interfering with the antenna coil's magnetic field and avoiding eddy currents.
2Loss of energy
If the sensor electrode is arranged on the outer periphery side of the core with winding direction along the longitudinal direction, then eddy current is avoided, but the door may unlock incorrectly when the user touches the outer side of the door handle
Solution Approach 1:
The sensor electrode is positioned to face only the inner side of the door handle, creating directional sensitivity. This local positioning ensures that capacitance changes are detected only when the user touches the intended area (inner side), preventing false unlocking from outer side contact while avoiding eddy currents through proper orientation.
Solution Approach 2:
The sensor electrode arrangement is made asymmetric by positioning it on the bobbin to detect only in one direction (toward the inner side of the door handle). This asymmetric configuration provides directional discrimination, allowing the system to distinguish between intentional inner-side touches and accidental outer-side touches.
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 antenna unit ensures reliable signal transmission and reception while preventing incorrect door unlocking by accurately detecting the user's touch on the inner side of the door handle, thus enhancing operational reliability.
Implementation Method 1
a sensor electrode coil to be wound on the bobbin to detect a predetermined state change based on a change in capacitance
Implementation Method 2
an antenna coil for effecting at least one of reception and transmission of an electromagnetic signal
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An antenna unit (1) includes: an antenna coil (2) for effecting at least one of reception and transmission of an electromagnetic signal; a bobbin (3) on which the antenna coil (2) is wound; a core (4) to be retained in the bobbin (3); and a sensor electrode coil (5) to be wound on the bobbin (3) to detect a predetermined state change based on a change in capacitance. The bobbin (3) includes: an antenna coil winding part (3a) on which the antenna coil (2) is wound; and an electrode coil winding part (3b) which protrudes from the antenna coil winding part (3a) in one direction and on which the sensor electrode coil (5) can be wound.