Flexible PCB Coil Assembly for Compact Movable Member Position Sensing
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Solution Overview
Problem
Conventional position sensing technologies for movable members, such as pistons and rotors, are expensive, complex, difficult to manufacture, and have large physical sizes with poor tolerances, making them unsuitable for many applications.
Innovation Solution
A flexible printed circuit board (FPCB) with coils printed on it is wrapped around a housing, featuring an excitation coil and sensing coils that detect the position of a movable member through changes in magnetic fields, allowing for precise and compact position sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional position sensing technologies are used, then position detection capability is achieved, but device size becomes large and manufacturing complexity increases
Solution Approach 1:
The patent replaces conventional mechanical position sensing technologies with a magnetic field-based sensing system. The movable member includes a magnet that generates a magnetic field, and the stationary coils detect position through magnetic field changes rather than mechanical contact or complex mechanical structures. This substitution eliminates the need for large mechanical sensor assemblies while maintaining accurate position detection capability.
Solution Approach 2:
The patent employs thin flexible printed circuit boards (FPCBs) with coils printed directly on them to create a compact sensing assembly. The FPCB can be wrapped around or mounted near the movable member in a space-efficient manner. This use of flexible thin-film technology allows the sensing system to achieve accurate position measurement while occupying minimal space compared to conventional rigid sensor assemblies.
2Measurement precision
If conventional position sensing technologies are used, then position detection capability is achieved, but manufacturing difficulty increases and tolerances worsen
Solution Approach 1:
The patent replaces complex mechanical positioning systems with a magnetic field-based sensing approach. The movable member incorporates a magnet that can be positioned using standard manufacturing techniques, and the stationary coils on the FPCB detect position through magnetic field interactions. This eliminates the need for precision mechanical assemblies, tight tolerances on moving parts, and complex alignment procedures required by conventional mechanical sensors.
Solution Approach 2:
The patent changes the fundamental sensing parameter from mechanical displacement to magnetic field characteristics. By detecting changes in magnetic field strength or distribution rather than measuring physical displacement mechanically, the system achieves accurate position detection through electrical measurements of magnetic field parameters. This parameter change enables the use of flexible FPCB manufacturing processes instead of precision mechanical machining and assembly.
3Measurement precision
If conventional position sensing technologies are used, then position detection is achieved, but cost increases
Solution Approach 1:
The patent merges the sensing coils directly onto a flexible printed circuit board, integrating multiple sensing elements into a single compact assembly. The FPCB can accommodate multiple coils for different sensing functions or redundant measurements, all mounted on one flexible substrate rather than requiring separate sensor housings and mounting structures. This merging reduces the overall device complexity and component count while maintaining accurate position detection capability.
Solution Approach 2:
The patent replaces complex mechanical sensor assemblies with an integrated magnetic field sensing system using FPCB-mounted coils. The magnet on the movable member interacts with the coils electrically rather than through mechanical linkages, eliminating the need for complex mechanical transmission elements, gear trains, or contact-based sensing mechanisms. This substitution simplifies the overall device architecture while achieving accurate position measurement.
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 FPCB configuration provides accurate position sensing with reduced size, improved manufacturing ease, and enhanced tolerance, enabling cost-effective and efficient control of movable members in various applications.
Implementation Method 1
the coils include at least one excitation coil and one sensing coil. As the movable member moves, linearly or rotationally, relative to the flexible printed circuit board, the coils detect the position of the movable member
Data Source
AI summary
An example assembly includes: a housing; a movable member configured to move within the housing; and a coil flexible printed circuit board (FPCB) wrapped around the housing, wherein the coil FPCB comprises: at least one excitation coil printed on the coil FPCB as a conductive track, wherein the excitation coil is configured to generate a magnetic field when an electric current is provided through the conductive track, and at least one sensing coil printed on the coil FPCB as a respective conductive track, wherein the magnetic field generated by the excitation coil is configured to induce a respective electric current in the at least one sensing coil, and wherein movement of the movable member within the housing changes a parameter associated with the respective electric current, thereby indicating a position of the movable member.