Tyre Tread Depth Sensing With Dual-Coil Temperature Compensation
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Solution Overview
Problem
Existing systems for measuring tread depth in pneumatic tires face challenges such as air tightness and rubber endurance issues due to protruding materials, and lack effective temperature compensation, leading to inaccurate measurements.
Innovation Solution
A system with a magnetic inlay embedded in the tire, featuring two coils with different inductances that are influenced by the magnetic inlay's size and temperature-dependent magnetic properties, allowing for wireless measurement and temperature compensation by calculating the ratio of inductances to infer tread depth wear, without protruding materials through the inner liner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If materials are protruding through the tyre inner liner to enable sensing, then sensing functionality is achieved, but air tightness and rubber endurance deteriorate
Solution Approach 1:
The sensing functionality is extracted from the tyre structure by using a separate sensor device with a coil and magnetic inlay that does not require protruding materials through the inner liner. The magnetic inlay is embedded in the tread surface while the coil remains inside the tyre, eliminating the need for protruding components and thus preserving air tightness and rubber endurance.
Solution Approach 2:
A magnetic field is introduced as an intermediary to transfer information about tread depth without requiring physical contact or protruding materials. The magnetic inlay modulates the magnetic field generated by the coil, allowing indirect measurement of tread depth while maintaining the integrity of the tyre structure.
2Device complexity
If single inductance measurement is used for simplicity, then device complexity is reduced, but temperature compensation capability is lost leading to measurement inaccuracy
Solution Approach 1:
The system uses two different inductance parameters (L1 and L2) measured by two coils with different geometries or positions. By measuring both inductances and calculating their ratio, the system compensates for temperature effects since both inductances are affected similarly by temperature, and the ratio cancels out the temperature dependency while preserving sensitivity to tread depth changes.
3Extent of automation
If electronic components are embedded in the tyre crown region, then wireless measurement capability is achieved, but mechanical strain and component destruction increase
Solution Approach 1:
The sensor device is segmented into two separate parts: the magnetic inlay embedded in the tread surface and the coil with electronic components positioned inside the tyre away from the crown region. This segmentation allows the electronic components to be protected from mechanical strain while still enabling wireless measurement functionality.
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 system provides accurate, temperature-independent tread depth monitoring, avoiding mechanical strain on electronic components and ensuring reliable operation, enabling timely tire replacement scheduling and economic benefits.
Implementation Method 1
The inventor has realised that the measured first and second inductance of the first and second coil are also dependent on temperature due to the temperature dependence of the magnetic properties of the magnetic inlay
Implementation Method 2
a first coil having a first inductance and a second coil having a second inductance. The first inductance is different from the second inductance and the first inductance and the second inductance are dependent at least in part on the size of the magnetic inlay
Data Source
Figure 1
AI summary
A system (8) for measuring tread depth of a pneumatic tyre is provided. The system (8) comprises a sensor element comprising a magnetic inlay (9) that is sized and shaped to be embedded in the tyre (1) and to have an outer surface (10) that is part of a rolling surface (4) of the tyre (1). The system (8) also comprises a first coil (11) having a first inductance, a second coil (12) having a second inductance, wherein the first inductance is different from the second inductance and the first inductance and the second inductance are dependent at least in part on the size of the magnetic inlay (9), an inductance measuring circuit (15) for measuring the first inductance of the first coil (11) and the second inductance of the second coil (12), wherein wear of the magnetic inlay (9) causes a change in the value of the measured first inductance and measured second inductance, the change being indicative of wear of the tread depth of the tyre (1), means to calculate the ratio of the values of the measured first inductance and of the second inductance (16), and a transmitter (17) for transmitting one or more output values that are representative of the measured first inductance and/or the measured second inductance and/or the ratio of the measured first inductance and the measured second inductance.