Magnetic Tire Tread Thickness Sensor Using Ferrite Field Localization
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Solution Overview
Problem
Existing systems for measuring the thickness of a tire's tread are either costly, require regular maintenance, or are unsuitable for tires with insufficiently conductive crown reinforcements, leading to inaccurate measurements due to interference from environmental factors and anisotropy of metal cords.
Innovation Solution
A system utilizing a sensor with a static magnetic field source, either a coil or permanent magnets, surrounded by high magnetic permeability materials like ferrite, which measures the distance between the rubber layer and its reinforcement, operating in reluctance mode to provide sensitive and localized thickness measurements, and is insensitive to metal cord orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If eddy current sensors are used to measure tread thickness, then measurement can be automated, but the system becomes unsuitable for tires with insufficiently conductive crown reinforcement
Solution Approach 1:
The patent changes the measurement parameter from electrical conductivity (eddy currents) to magnetic permeability. By using a static magnetic field source and measuring field strength variations, the system can measure tread thickness on tires with metal reinforcement that has insufficient electrical conductivity for eddy current methods.
Solution Approach 2:
The patent replaces the electromagnetic induction principle (eddy currents) with a static magnetic field principle. Instead of using alternating magnetic fields that induce eddy currents, the system uses a static magnetic field whose strength is measured directly, substituting one electromagnetic mechanism for another that works with magnetically conductive but electrically non-conductive materials.
2Extent of automation
If optical systems with cameras or lasers are used for measurement, then automated measurement is achieved, but the systems become costly and require regular maintenance
Solution Approach 1:
The patent employs a simpler magnetic sensor system that is less costly than optical systems with cameras or lasers. The static magnetic field source and field strength sensor constitute a more economical solution that requires less maintenance and does not need to be embedded in the roadway infrastructure.
Solution Approach 2:
The patent uses magnetic field lines as an intermediary to measure tread thickness. Instead of directly observing the tread surface with cameras or lasers, the system measures the distortion of magnetic field lines caused by the tread's magnetic permeability and thickness, providing an indirect but effective measurement method.
3Ease of operation
If eddy current measurement systems are used, then measurement can be performed on roadway, but the measurements are affected by environmental factors and anisotropy of metal cords
Solution Approach 1:
The patent changes from measuring electrical effects (eddy currents) to measuring magnetic field strength. This parameter change makes the measurement insensitive to the electrical conductivity variations and anisotropy of metal cords, while remaining sensitive to the magnetic permeability differences that indicate tread thickness.
Solution Approach 2:
The patent converts the magnetic permeability of the metal reinforcement, which causes problems for eddy current measurements, into a useful feature. The magnetically conductive material enhances the magnetic field signal, improving measurement sensitivity rather than degrading it.
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 offers precise, low-power, and maintenance-free measurements of tire tread thickness, suitable for various vehicle types, including those with metal-reinforced tires, by localizing magnetic field lines and improving sensitivity, while being insensitive to anisotropy and environmental interference.
Implementation Method 1
the sensor comprises a static magnetic field source and a sensitive element whose output signal is a function of the level of the local magnetic field
Implementation Method 2
the layer comprising a face joined to an adjacent reinforcement made with at least one material having a magnetic permeability greater than the magnetic permeability of air
Implementation Method 3
the coil surrounds, or is surrounded by, a material having high magnetic permeability and low electrical conductivity, such as a ferrite. The presence of the ferrite makes it possible to localize the magnetic field lines
Implementation Method 4
systems for measuring the thickness of the tread of a tyre, comprising sensors sensitive to the eddy currents generated by an exciting magnetic field in the crown reinforcement of the tyre
Implementation Method 5
sensors sensitive to the eddy currents generated by an exciting magnetic field
Data Source
AI summary
A system for measuring a thickness of a layer of rubber material of a tire includes a sensor. The layer includes a joined face, which is joined to an adjacent metal reinforcement, and a free face, which is in contact with air. The sensor, which measures a distance d between the joined face and the free face, includes a source of a static magnetic field and a sensitive element whose output signal is a function of a level of a local magnetic field. The sensor is positioned in such a way that a magnetic field strength measured by the sensitive element varies when the distance d decreases.