Bearing Sensor Assembly with Directional Coupler
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Solution Overview
Problem
Existing wireless temperature sensors for bearing cages face challenges with low signal-to-noise ratio and microphony due to impedance mismatching, making it difficult to accurately measure temperature in harsh environments and smaller bearings.
Innovation Solution
A sensor assembly with a directional coupler and a current mode balun is integrated into the bearing cage, allowing for improved signal reflection and reduced microphony by balancing the coaxial cable, enhancing the signal-to-noise ratio and enabling reliable energy and data transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a passive wireless temperature sensor is integrated into the bearing cage using flux coupling between coils, then temperature measurement capability is achieved, but the signal to noise ratio becomes low
Solution Approach 1:
The patent introduces a directional coupler as an intermediary device between the primary coil and the analysis circuit. This coupler selectively extracts the reflected signal portion while isolating it from the primary coil, thereby improving the signal to noise ratio without compromising temperature measurement capability
Solution Approach 2:
The patent segments the signal path by separating the reflected signal extraction function from the primary coil using a directional coupler. This segmentation allows the reflected signal to be routed to a dedicated analysis circuit, improving signal quality and measurement precision
2Measurement precision
If a passive wireless temperature sensor is integrated into the bearing cage using coaxial cable, then temperature measurement capability is achieved, but microphony occurs due to impedance mismatching
Solution Approach 1:
The patent introduces a current mode balun as an intermediary device that acts as an impedance transformer. It converts the unbalanced coaxial cable impedance to match the balanced primary coil impedance, thereby eliminating microphony caused by impedance mismatching while preserving temperature measurement capability
Solution Approach 2:
The patent changes the impedance parameter of the coaxial cable system by introducing a current mode balun. This device transforms the impedance characteristics to achieve proper matching between the unbalanced cable and balanced coil, eliminating harmful microphony effects
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 solution provides a reliable and accurate temperature measurement with improved signal-to-noise ratio and reduced sensitivity to environmental changes, effectively addressing the limitations of previous technologies.
Implementation Method 1
the inductor coil interacts with the primary coil of the driven oscillator circuit
Implementation Method 2
a passive oscillator circuit including a temperature dependent capacitance and an inductor coil
Data Source
AI summary
The invention relates to a sensor assembly for use in a bearing including at least one bearing cage configured to accommodate at least one rolling element of the bearing, the sensor assembly including a driven oscillator circuit providing a receiver, a function generator and a primary coil, and a passive oscillator circuit including a temperature dependent capacitance. The passive oscillator circuit is configured to be attached to the bearing cage such that the inductor coil interacts with the primary coil of the driven oscillator circuit. It is proposed that a directional coupler is provided in a signal line between a function generator and the primary coil of the system, wherein the directional coupler is arranged to output a signal reflected from the passive resonant circuit in the cage toward a tuned receiver receiving the feedback of the signals generated by the function generator.