Valve Stem Capacitive Sensor for Tire Pressure Monitoring
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Solution Overview
Problem
Existing tire pressure measurement systems are difficult to install and maintain, vulnerable to damage, and require components to be positioned inside the tire wall, making them inaccessible and unreliable.
Innovation Solution
A valve stem with an integrated capacitive pressure sensor and inductive coil, allowing for easy installation and maintenance, with the coil located either inside or outside the stem, and capable of measuring pressure and temperature, with the option for multiple sensors and interchangeable components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If components are positioned inside the tyre wall to measure pressure, then pressure measurement is achieved, but installation becomes difficult and components become vulnerable to damage
Solution Approach 1:
The measuring circuit is extracted from the tyre wall and relocated to the valve stem, which is externally accessible. This allows the components to be installed and maintained easily while still measuring tyre pressure through the air inside the tyre, resolving the contradiction between durability and installation ease.
Solution Approach 2:
The valve stem acts as an intermediary structure that provides external access to the tyre's internal pressure. By placing the measuring circuit in the valve stem rather than embedding it in the tyre wall, the system achieves both easy installation and reliable operation.
2Reliability
If components are positioned inside the tyre wall, then pressure measurement is possible, but accessibility for maintenance is reduced
Solution Approach 1:
The measuring circuit is extracted from the inaccessible tyre wall and placed in the easily accessible valve stem. This enables straightforward maintenance and replacement while maintaining measurement functionality through the tyre's internal air pressure.
3Measurement precision
If the inductive coil is located inside the valve stem, then electromagnetic shielding from metal components is avoided, but the coil becomes vulnerable to damage
Solution Approach 1:
The valve stem is designed with a specific recess region that provides both electromagnetic transparency for accurate signal measurement and mechanical protection for the coil. This localized structural feature resolves the contradiction between measurement precision and component protection.
4Object-affected harmful factors
If a recess is provided to protect the coil, then the coil is protected from damage, but the device structure becomes more complex
Solution Approach 1:
The protective recess is integrated into the valve stem structure itself rather than being a separate component. This merging of protection function into the existing structure provides coil protection while minimizing additional structural complexity.
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
Enables simple, durable, and remote monitoring of tire pressure and temperature, reducing installation complexity and enhancing maintenance accessibility while protecting the coil from damage.
Implementation Method 1
The circuit comprises a capacitive pressure sensor and an inductive coil. The inductive coil is coiled around the valve stem.
Implementation Method 2
The natural frequency is measured by inductive coupling to coils outside the tyre.
Implementation Method 3
The natural frequency of the disclosed circuit depends on the capacitive value of the circuit which changes with changes in pressure in the tyre.
Data Source
AI summary
This invention provides a valve stem (21) for a tire. The valve stem (21) comprises at least one electrical circuit for measuring pressure within the tire. The circuit comprises a capacitive pressure sensor (5) and an inductive coil (6). The inductive coil (6) is coiled around the valve stem (21).