Proximity Sensor Filler and Shielding for Noise-Resistant Detection
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Solution Overview
Problem
Existing proximity sensors face issues with noise interference due to capacitive coupling of fillers and power supply cables, leading to decreased detection accuracy when detecting objects at increased distances.
Innovation Solution
The proximity sensor incorporates a detection coil housed in a metal head housing filled with a filler mixture of adhesive and an additive with lower relative permittivity, along with a conductive shield and separate amplifier board, to minimize capacitive coupling and noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the detection distance is increased, then the detection range is improved, but the detection accuracy decreases due to weak magnetic field changes and noise interference
Solution Approach 1:
A noise prevention member (shielding structure) is introduced as an intermediary between the power supply cable and the detection coil. This shielding structure blocks noise current from reaching the detection coil, thereby maintaining detection accuracy even when the detection distance is increased and the magnetic field change becomes weaker.
2Strength
If a filler is used to improve mechanical strength, then the structural strength is improved, but noise current penetrates the insulating member due to capacitive coupling of the filler
Solution Approach 1:
A noise prevention member is placed between the power supply cable and the detection coil to block noise current. This intermediary structure prevents capacitive coupling noise from reaching the detection coil while allowing the filler to maintain mechanical strength throughout the head shaft body.
Solution Approach 2:
The relative permittivity of the filler material is optimized to reduce capacitive coupling effects. By selecting a filler with appropriate dielectric properties, the noise current generation is minimized while maintaining the mechanical strength and filling functions.
3Object-affected harmful factors
If an insulating member is disposed to prevent noise current, then the noise prevention is improved, but the noise current penetrates due to capacitive coupling of the filler
Solution Approach 1:
A dedicated noise prevention member (shielding structure) is introduced as an intermediary barrier between the power supply cable and detection coil. This shielding structure provides effective noise current blocking that is not compromised by the capacitive coupling effects of the filler material.
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 detection accuracy by reducing noise current influence on the detection coil, allowing for longer detection distances while maintaining mechanical strength and reducing manufacturing complexity.
Implementation Method 1
a detection coil 1 that generates a detection current
Implementation Method 2
the noise current penetrates the insulating member due to capacitive coupling of the filler
Data Source
AI summary
The proximity sensor includes a detection coil, a metal head housing, and a power supply cable. The detection coil generates a detection current. The metal head housing houses the detection coil. The power supply cable has an electrical connection with the detection coil and is connected to the metal head housing. At least a part of an internal space of the metal head housing is filled with a filler so as to bury the detection coil. As the filler, an adhesive and an additive having a relative permittivity lower than that of the adhesive are mixed.