Magnetic Reluctance Sensor for Tire Tread Thickness Measurement
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Solution Overview
Problem
Existing systems for measuring tire tread thickness are not precise and sensitive due to their sensitivity to the electrical conductivity of tire crowns, which varies by tire type and usage, and are often disturbed by environmental factors like dirt and water.
Innovation Solution
A system using a sensor with an alternating magnetic field source and a coil sensitive to magnetic flux density variations, operating in reluctant mode with a lower excitation frequency, which reduces eddy current detection and enhances sensitivity to distance changes, allowing for accurate tread thickness measurement regardless of tire conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If eddy current-based sensors are used to measure tread thickness, then measurement can be performed on tire reinforcement, but measurement precision deteriorates due to sensitivity to electrical conductivity variations in different tire types and usage conditions
Solution Approach 1:
The patent changes the operating parameters of the sensor by using lower excitation frequencies (below 10 kHz) and adjusting excitation power levels. This parameter change transforms the sensor's response characteristics from being dominated by eddy currents to being dominated by magnetic reluctance effects, thereby eliminating sensitivity to electrical conductivity variations while maintaining measurement capability on tire reinforcement
Solution Approach 2:
The patent substitutes the measurement mechanism from eddy current-based detection to magnetic reluctance-based detection. By measuring changes in magnetic field penetration through the rubber layer rather than electrical currents induced in the reinforcement, the system achieves measurement precision independent of the reinforcement's electrical conductivity properties
2Reliability
If high frequency excitation is used in magnetic field sensors, then eddy current detection is enhanced, but sensitivity to distance changes decreases and common mode noise increases
Solution Approach 1:
The patent uses periodic alternating magnetic field excitation at specific low frequencies (below 10 kHz) to probe the magnetic properties of the rubber layer. This periodic action at optimized frequencies maximizes the sensor's sensitivity to distance changes while minimizing eddy current interference and common mode noise, achieving precise tread thickness measurement
3Extent of automation
If optical measurement systems are embedded in the roadway, then automated tread depth measurement is achieved, but device complexity and maintenance requirements increase
Solution Approach 1:
The patent extracts the measurement function from complex embedded roadway infrastructure and places it in a portable, handheld sensor device. This extraction eliminates the need for roadway embedding, reduces device complexity, and simplifies maintenance while maintaining automated measurement capability through portable operation
Solution Approach 2:
The patent enables the measurement system to be self-contained and portable, allowing operators to manually position the sensor on tires without requiring infrastructure installation or complex setup. The device performs measurements autonomously once positioned, providing automated measurement functionality without the complexity of embedded roadway systems
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 system provides precise and sensitive measurements of tire tread thickness, reducing common mode noise and allowing for non-invasive, portable operation without significant speed limitations, thus improving tire wear monitoring accuracy and reliability.
Implementation Method 1
a sensor placed in the box capable of measuring the distance d between the bonded face and the free face of the layer of rubbery material. The sensor comprises an alternating magnetic field source and an element sensitive to the variation of the magnetic flux density in the vicinity of said source coil
Implementation Method 2
the frequency and excitation power of the source coil are such that the magnetic flux density increases between the adjacent armature and the source coil, when the distance d decreases
Implementation Method 3
The sensor of the measuring system according to an object of the invention has the advantage of operating in reluctant mode, therefore with, at a given power, a lower excitation frequency of the coil than in the case of a similar sensor operating in a mode sensitive to eddy currents
Data Source
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AI summary
The invention relates to a system for measuring the thickness of a layer of rubbery material of a tyre comprising one face connected to an adjacent metal frame and one free face in contact with the air, the system comprising a housing with an application face intended to be in contact with the free face of the layer and a sensor placed in the housing capable of measuring the distance d between the connected face and the free face of the layer of rubbery material, such that, the sensor comprising an alternating magnetic field source and an element sensitive to the variation in the magnetic flux density near the source winding, the source is a winding and the sensitive element is a second winding, and such that the frequency and excitation power of the source winding are such that the magnetic flux density increases between the adjacent frame and the source winding, when the distance d decreases.