Shielded Proximity Sensor Coil Layout for Embedded Metal Interference
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Solution Overview
Problem
Proximity sensors fail to sufficiently extend detection distance due to the influence of embedded metals, which interfere with the detection of weak changes in reception waveforms.
Innovation Solution
A proximity sensor design incorporating a first and second concentrically arranged coil, a ferrite core, a reception circuit, a control circuit, and an electric shield with a radial cut, which suppresses the influence of embedded metals by guiding magnetic fields and detecting changes in voltage or current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the detection distance is extended to avoid contact with the detection object, then the proximity sensor can prevent contact, but the sensor cannot sufficiently detect weak changes in the reception waveform due to embedded metal interference
Solution Approach 1:
An electric shield is introduced as an intermediary component between the coil and the embedded metal. The shield includes a conductive plate with a through-hole that blocks electromagnetic interference from the embedded metal while allowing the magnetic field to pass through to the detection object, thus enabling detection distance extension without losing detection accuracy
Solution Approach 2:
The electric shield is selectively positioned only in the region where embedded metal interference occurs, with a through-hole that allows the magnetic field to pass through to the detection object. This localized approach suppresses interference while maintaining detection capability in the specific direction toward the detection object
2Ease of manufacture
If the proximity sensor is embedded in metal components (nuts and washers), then the sensor can be integrated into the mechanical assembly, but the embedded metal interferes with detecting weak changes in the reception waveform
Solution Approach 1:
The electric shield acts as a mediator that separates the coil from the embedded metal components. The shield blocks the harmful electromagnetic interference from the embedded metal while allowing the useful magnetic field to pass through to the detection object, enabling the sensor to be embedded in metal assemblies without performance degradation
Solution Approach 2:
The electric shield extracts and isolates the interference problem by creating a separate zone between the coil and embedded metal. The shield's conductive plate with through-hole design extracts the interference blocking function while maintaining magnetic field transmission, allowing the sensor to function properly when embedded in 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
The design effectively extends the detection distance by accurately distinguishing between detection objects and embedded metals, improving detection accuracy and reducing interference.
Implementation Method 1
The coil generates a magnetic field by an excitation current
Implementation Method 2
The ferrite core guides a magnetic field generated from the coil
Implementation Method 3
The electric shield has a bottomed cylindrical shape disposed outside the second coil in the radial direction. The electric shield includes a peripheral portion and a detection surface portion
Data Source
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AI summary
Provided is a proximity sensor capable of sufficiently extending a detection distance by suppressing an influence of embedded metal. The proximity sensor includes a first coil, a second coil, a transmission circuit, a ferrite core, a reception circuit, a control circuit, and an electric shield. The second coil disposed radially outside the first coil. The transmission circuit periodically applies a pulsed excitation current to at least one of the coils. The control circuit detects the detection object D based on the change in the detected voltage or current generated in at least one of the coils by the magnetic field. The electric shield is a press-molded product having a bottomed tubular shape disposed outside the second coil in the radial direction and having a peripheral portion and a detection surface portion in which a cut crossing a direction around an axis is formed.