Inductive Sensor Coils Axial Gap for Rotational Angle
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Solution Overview
Problem
Existing inductive rotation sensors lack sufficient measurement sensitivity, which limits their accuracy in detecting rotational positions.
Innovation Solution
The design involves two coaxially arranged coils with an axial gap, where a ferromagnetic influencing element is introduced to change the self-inductance and mutual inductance based on its rotational position, generating a measurement signal dependent on displacement or angle of rotation, with the coils connected in series and excited by AC voltage to enhance sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single coil is used in existing inductive rotation sensors, then the sensor structure is simple, but the measurement sensitivity is insufficient
Solution Approach 1:
The sensor is divided into two separate coils (first coil and second coil) arranged coaxially with an axial gap between them. This segmentation allows each coil to independently interact with the ferromagnetic influencing element, thereby increasing the measurement sensitivity while maintaining a relatively simple overall structure.
Solution Approach 2:
The patent introduces a spatial dimension by arranging two coils at different positions along the coil axis with an axial gap between them. This dimensional arrangement enables the influencing element to be immersed in the gap, creating a measurable change in mutual inductance that enhances sensitivity without significantly increasing structural complexity.
2Measurement precision
If the influencing element is made of ferromagnetic material, then the relative change in mutual inductance is greater, but the coupling between coil inductances is weakened
Solution Approach 1:
The ferromagnetic influencing element acts as an intermediary between the two coils. When the influencing element is immersed in the axial gap, it mediates the magnetic field interaction between the coils, causing a measurable change in mutual inductance that enhances sensitivity while the ferromagnetic material's high permeability naturally provides stable coupling.
3Adaptability or versatility
If two coils are arranged coaxially with an axial gap, then the sensor can measure rotational angles up to 360 degrees, but the device complexity increases
Solution Approach 1:
The coaxial arrangement of two coils with an axial gap creates a universal measurement structure that can detect rotational angles across the full 360-degree range. The symmetric geometry and magnetic field distribution enable the sensor to measure any rotational position, providing multi-functionality without requiring complex additional components.
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 configuration results in a more sensitive and robust sensor with a greater relative change in mutual inductance compared to self-inductance, allowing for precise measurement of rotational angles up to 360 degrees, suitable for applications like vehicle level control.
Implementation Method 1
The coils (2, 4) can be excited, for example, by a microprocessor which feeds square-wave, sinusoidal or any desired pulses from an AC voltage source into the coils (2, 4). The total inductance of the coils (2, 4) can then be determined from the duration of the decay of the pulse to a lower limit value.
Implementation Method 2
The influencing element (8) is made of a ferromagnetic material, at least in the area where it overlaps with the two coils (2, 4).
Implementation Method 3
The introduction of the influencing element (8), which is at least partially made of a magnetic material, into the space between the coils (2, 4) affects the self-inductance of the coils (2, 4) and the mutual inductance.
Data Source
Figure 1~2
Figure 3~5
Figure 4a~4c
AI summary
The invention relates to an inductive displacement or rotational angle sensor (1) comprising at least one electrical coil (2, 4), which is provided with turns, as well as an influencing element (8) which interacts with said coil and, depending on its position, gives rise to a different inductance (L1, L2, M) of the at least one coil (2, 4). The invention provides at least two separate coils (2, 4) which are arranged coaxially with respect to a coil axis (9) and have an axial interspace (18) into which the influencing element (8) can be immersed with a degree of overlap with the magnetic fields which are generated by the coils (2, 4), which degree of overlap is dependent on the position of the influencing element.