Ring Magnet Recess for Constant Ellipticity
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Solution Overview
Problem
Magnetic sensors used for rotational angle detection on rotatable shafts face inaccuracies due to misalignment and changes in assembly tolerances, wear, and mechanical loads, which affect the measurement of magnetic field components, leading to inconsistent ellipticity and inaccurate angle determination.
Innovation Solution
A ring magnet with a recess in its circumferential surface is used, ensuring a constant ellipticity of the magnetic field components measured by the sensor, even when the magnet moves along the rotational axis, thereby maintaining accurate rotational angle detection despite positional changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard ring magnet is used without a recess, then the structure is simple and easy to manufacture, but the ellipticity of the magnetic field varies when the magnet moves along the rotational axis, leading to inaccurate rotational angle detection
Solution Approach 1:
A recess is introduced into the circumferential surface of the ring magnet, creating an asymmetric structure. This asymmetric geometry is specifically designed to compensate for the magnetic field variations that occur when the magnet moves along the rotational axis, thereby maintaining constant ellipticity and improving rotational angle detection accuracy
Solution Approach 2:
The recess is positioned at a specific location on the circumferential surface of the ring magnet to locally modify the magnetic field distribution. This localized structural change creates a specific magnetic field pattern that ensures constant ellipticity is maintained during axial movement, improving measurement precision without requiring complete redesign of the entire magnet
2Measurement precision
If assembly tolerances and mechanical loads are minimized to maintain alignment, then measurement accuracy improves, but manufacturing constraints and device rigidity are compromised
Solution Approach 1:
The recess in the ring magnet pre-compensates for the effects of assembly tolerances and mechanical loads. By designing the magnet structure with the recess, the system inherently compensates for potential misalignments and variations during operation, reducing the stringency of manufacturing precision requirements while maintaining measurement consistency
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 allows for robust and accurate determination of rotational angles by maintaining a constant ellipticity of the magnetic field, reducing inaccuracies caused by misalignment and mechanical changes, ensuring reliable angle measurement within a tolerance range.
Implementation Method 1
a magnetic sensor to measure a substantially constant ellipticity of a radial component of a magnetic field of the ring magnet and a tangential component of the magnetic field of the ring magnet
Data Source
AI summary
A ring magnet for use in determining a rotational angle of a rotatable shaft and configured to be connected to the rotatable shaft for co-rotation with the rotatable shaft around a rotational axis may include a recess in a circumferential surface of the ring magnet, where the recess may be recessed away from the circumferential surface to cause a magnetic sensor to measure a substantially constant ellipticity of a radial component of a magnetic field of the ring magnet and a tangential component of the magnetic field of the ring magnet, when measuring the rotational angle of the rotatable shaft, as the ring magnet moves along the rotational axis of the rotatable shaft.