Offset Planar Coils for Soiling-Resistant Speed Detection
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Solution Overview
Problem
Existing inductive speed detection technologies are sensitive to soiling by particles, have a deep installation depth, and are limited by a short distance to the generator, making them unsuitable for high-temperature and high-pressure applications.
Innovation Solution
The use of two spatially offset planar coils with a pulse wheel, which can be toothed or lattice structured, allows for precise frequency evaluation, reducing sensitivity to soiling and enabling a greater distance between the sensor and pulse wheel, with the option for coding the pulse wheel to differentiate teeth for rotational direction detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Hall sensor elements are used for speed detection, then the sensor is inexpensive and can operate at high temperatures, but it becomes sensitive to dirt particles and may fail entirely when soiled
Solution Approach 1:
The patent replaces the Hall sensor (which detects magnetic field variations) with an inductive sensor that uses coils to detect variations in magnetic flux. This substitution eliminates the sensitivity to dirt particles while maintaining the ability to detect speed through magnetic field variations. The inductive coil design inherently resists contamination from dirt, oil, and water.
2Measurement precision
If wound coils are used for inductive speed detection, then the sensor can detect magnetic field variations, but it requires several centimeters installation depth and has high material expense
Solution Approach 1:
The patent changes the geometric parameters of the coil by using a planar (flat) configuration instead of traditional wound coils. This parameter change reduces the installation depth from several centimeters to a much shallower depth while maintaining the inductive sensing capability for speed detection. The planar coil design achieves the same magnetic field variation detection with reduced spatial requirements.
3Measurement precision
If traditional inductive sensors are used, then speed detection is possible, but the distance to the generator is limited
Solution Approach 1:
The patent replaces traditional inductive sensors with a planar coil design that detects magnetic field variations through the pulse wheel. This substitution enables greater distance to the generator by improving the magnetic field coupling efficiency and reducing the sensor's spatial requirements, allowing accurate speed detection at extended distances.
4Measurement precision
If frequency evaluation is used instead of voltage or current evaluation, then measurement precision is improved, but the complexity of the evaluation circuit increases
Solution Approach 1:
The patent uses frequency evaluation with feedback mechanisms to detect speed. The evaluation circuit monitors the frequency of signals generated by the pulse wheel and uses this information to determine speed. This feedback approach provides higher resolution and more precise speed measurement compared to direct voltage or current evaluation, while the circuit complexity is managed through efficient frequency counting and comparison techniques.
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 solution provides a robust, precise, and temperature-stable speed detection system that is resistant to soiling and can operate at greater distances, enhancing reliability and flexibility in applications like transmissions.
Implementation Method 1
inductive sensor elements are also well suited for detecting variations in a magnetic field
Implementation Method 2
The pulse wheel does not have to be coded to be able to detect the direction in which it rotates. What is determinant for this, is that the two planar coils are arranged spatially offset in the direction of rotation
Data Source
AI summary
A device for inductive speed detection includes two planar coils which are arranged offset at a given distance from a pulse wheel and in the rotational direction of the pulse wheel, and are each part of an oscillator, the oscillator frequency of which is evaluated.