Rotary Shaft Axial Sensing via Single-Coil Air-Gap Detection
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Solution Overview
Problem
Existing axial detectors for rotating shafts in rotating machines suffer from poor linearity, increased axial dimensions, complex adjustments, and high manufacturing costs due to the need for compensation coils and mechanical centering.
Innovation Solution
A device with an induction coil and a fixed magnetic circuit, powered by an alternating voltage source and a capacitor, which eliminates the need for a compensation coil and mechanical centering, providing improved linearity and simplified production by using a capacitor to detect changes in the air gap between the target and the induction coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a compensation coil is used to improve detection accuracy, then measurement precision is improved, but device complexity and axial dimensions increase
Solution Approach 1:
The patent removes the compensation coil from the detector structure, extracting the problematic element that caused complexity and axial dimension increases. The invention achieves accurate detection using only a single induction coil by measuring inductance variations directly, eliminating the need for the compensation coil and its associated mechanical adjustment mechanisms.
Solution Approach 2:
The patent replaces the mechanical adjustment system (peelable shims for centering) with an electrical measurement approach. By measuring inductance variations of a single coil, the system achieves accurate axial position detection without mechanical centering adjustments, substituting mechanical complexity with electrical measurement simplicity.
2Measurement precision
If a compensation coil and peelable shim are used for mechanical centering, then detection accuracy is improved, but manufacturing cost and production complexity increase
Solution Approach 1:
The patent removes the peelable shim and compensation coil components, extracting the elements that increase manufacturing cost and production complexity. The simplified structure with a single induction coil requires fewer parts, less assembly work, and eliminates expensive mechanical adjustment mechanisms.
Solution Approach 2:
The patent replaces expensive mechanical adjustment components (peelable shims, precision-machined compensation coil assemblies) with a simple electrical measurement system. The single induction coil design uses inexpensive components that are easier to manufacture and assemble, reducing overall production costs.
3Device complexity
If a single induction coil is used without compensation, then device complexity is reduced, but measurement precision deteriorates due to non-linearity
Solution Approach 1:
The patent measures inductance variations (L) of the induction coil as the shaft moves axially. By monitoring changes in inductance rather than using complex mechanical or electrical compensation mechanisms, the system achieves linear detection characteristics. The inductance change is directly proportional to axial displacement, providing inherent linearity without compensation coils.
4Measurement precision
If mechanical centering with peelable shims is performed, then detection accuracy is improved, but ease of operation and assembly are worsened
Solution Approach 1:
The patent removes the peelable shim mechanism entirely, eliminating the need for mechanical centering operations. The single induction coil design inherently provides accurate detection without requiring manual adjustment or special assembly procedures for centering the detector.
Solution Approach 2:
The detection system performs self-alignment through electrical measurement. The inductance measurement automatically adapts to the axial position of the shaft, eliminating the need for manual mechanical centering by operators during assembly or maintenance operations.
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 achieves better detection linearity, reduces manufacturing costs, and simplifies the production process by eliminating the need for mechanical adjustments and compensation coils, while maintaining effective axial position detection.
Implementation Method 1
an induction coil associated with a fixed magnetic circuit secured to the stator of the rotating machine and arranged facing said target while leaving an air gap
Data Source
Figure 1~3
Figure 4
Figure 5~7
AI summary
The device has an alternating current voltage source (1) i.e. simple oscillator, connected between an end (7) of an induction coil (31) and a point (6) at reference voltage. A capacitor (2) is connected between the end and another end (8) of the coil. A shunt current detection device (4) is interposed between the latter end and the point to deliver information about a magnitude of detection current (Isense) flowing between the latter end and the point on a line (5), where the information represents a value of modification to width of air gap presenting a preset nominal value. The device has a target of ferromagnetic material e.g. ferrite, placed at an end of a rotary shaft. The induction coil is associated with a stationary magnetic circuit made of ferrite. Connection wires of the induction coil are arranged in a space filled with epoxy resin. An independent claim is also included for a turbo-molecular vacuum pump.