Sensor Device Axial Position Determination Using Radial Coils
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Solution Overview
Problem
Existing sensor devices for determining axial and rotary positions of a body face challenges, including the need for sensor coils to be axially aligned with a flange surface and the inability to determine rotary positions of rotationally symmetric bodies without notches, which complicates assembly and interferes with axial position determination.
Innovation Solution
A sensor device comprising at least one excitation coil and two detection coils arranged in perpendicular planes, allowing for axial position determination by analyzing signal differences between the coils, with additional coils and magnetic field sensors enabling determination of radial and tilt positions, and rotary position detection without the need for notches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensor coils are arranged axially opposite a flange surface to determine axial position, then axial position determination is enabled, but assembly becomes difficult and the coils cannot be moved axially past the flange surface
Solution Approach 1:
The patent transitions from axial arrangement of sensor coils to a radial arrangement where coils are positioned in the radial direction rather than axially opposite the flange. This dimensional change allows the coils to sense axial position through radial placement, eliminating the assembly difficulty while maintaining measurement capability.
Solution Approach 2:
The patent employs asymmetric coil arrangements where coils are positioned at different radial distances and angular positions around the rotor. This asymmetric configuration enables axial position determination through differential sensing, avoiding the need for symmetric axial alignment that causes assembly problems.
2Measurement precision
If a notch is provided on the thrust disk or shaft to determine rotary position, then rotary position detection is enabled, but it interferes with axial position determination and complicates the structure
Solution Approach 1:
The patent makes the sensor coils serve multiple functions: the same radially arranged coils that detect axial position also detect rotary position through their differential signals. This eliminates the need for separate notches or features on the rotor, reducing structural complexity while maintaining both measurement capabilities.
Solution Approach 2:
The patent combines axial position sensing and rotary position sensing into a single sensor system using radially arranged coils. The same coil arrangement and signal processing mechanism handle both types of position detection, merging two functions into one integrated system.
3Measurement precision
If multiple pickup coils are placed at different angular positions to increase sensitivity, then measurement sensitivity is improved, but the device complexity increases
Solution Approach 1:
The patent divides the sensing function across multiple radially arranged coil pairs positioned at different angular positions. Each pair contributes to both axial and rotary position detection, with the segmented arrangement providing sensitivity through spatial distribution rather than through increasing the total number of coils.
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 flexible and sensitive method for determining axial, radial, tilt, and rotary positions of a body, simplifying assembly and eliminating the need for axial alignment of sensor coils, while maintaining high sensitivity and rotational symmetry.
Implementation Method 1
A high-frequency current is fed to the excitation coil, thus generating a high-frequency magnetic field. Eddy currents are generated in the conductive body as a result of the high-frequency magnetic field.
Implementation Method 2
Eddy currents are generated in the conductive body as a result of the high-frequency magnetic field. The eddy currents prevent the high-frequency magnetic field from entering the bulk of the body.
Implementation Method 3
A plurality of pickup coils or other magnetic field sensors are placed in the vicinity of the excitation coil at different angular positions along the circumference of the body. These changes are picked up by the pickup coils.
Data Source
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AI summary
A sensor device for determining an axial position of a body (10) along a longitudinal axis (A) comprises an excitation coil (23) that extends around the longitudinal axis, one or more first detection coils (21) arranged in the vicinity of the excitation coil in a first detection plane (P1), and one or more second detection coils (22) arranged in the vicinity of the excitation coil in a second detection plane (P2). Excitation circuitry supplies the excitation coil (23) with current at an excitation frequency to create an excitation magnetic field distribution. Detection circuitry determines the axial position of the body based on signals from the first and second detection coils at the excitation frequency. The detection circuitry bases the determination of the axial position on at least one difference between the signals from the first detection coils and the signals from the second detection coils. A rotary position of the body can be determined by detecting a stray magnetic field of a magnet carried by the body, using at least two magnetic field sensors (24). The magnetic field sensors are arranged on a common printed circuit board (25) with the excitation and detection coils.