Rotation Angle Sensor With Concave Magnet And Multi-Directional Detection
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Solution Overview
Problem
Conventional rotation angle sensing devices experience detection errors due to shaft wobble and minute movements of magnets, leading to inaccurate measurement of rotation angles, especially when only radial magnetic flux is detected, and variations in magnetic flux intensity cause further errors.
Innovation Solution
A rotation angle sensing device with a magnet having a concave side surface orthogonal to the rotary shaft, where the magnetic sensor is placed to detect identical amplitudes of magnetic field intensity in both radial and circumferential directions, reducing detection errors by utilizing a TMR, GMR, or AMR element and arranging multiple sensor parts at specific intervals to minimize high-frequency errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single magnet is used with a magnetic sensor element arranged at the outer circumference to detect radial magnetic flux, then the device structure is simple, but detection errors are accentuated due to shaft wobble and minute movement of the magnet
Solution Approach 1:
The magnet is divided into multiple segments (first magnet and second magnet) arranged at different radial positions. This segmentation allows the magnetic sensor to detect magnetic flux from multiple sources, creating a closed magnetic field pattern that reduces sensitivity to positional variations caused by shaft wobble and minimizes detection errors.
2Device complexity
If magnetic sensor elements are arranged to detect only radial magnetic flux, then the magnetic field configuration is simple, but detection accuracy is insufficient and errors are accentuated when positions shift
Solution Approach 1:
The invention transitions from detecting only radial magnetic flux to detecting magnetic flux in multiple dimensions (radial and circumferential components). By arranging magnets at different radial positions and using magnetic sensor elements that can detect flux from multiple directions, the system creates a more robust detection mechanism that compensates for positional shifts and improves accuracy.
3Power
If the magnetic sensor is positioned to detect maximum magnetic flux intensity, then the signal strength is high, but detection errors are accentuated when radial positions of magnets shift
Solution Approach 1:
The invention changes the operational parameters by detecting magnetic flux in multiple directions (radial and circumferential components) rather than relying solely on maximum radial flux intensity. This parameter change allows the system to maintain high signal strength while reducing sensitivity to radial position shifts, as the multi-component detection approach compensates for positional variations.
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 enables accurate detection of rotation angles by maintaining consistent magnetic field intensity in both radial and circumferential directions, reducing errors caused by shaft wobble and improving detection precision.
Implementation Method 1
a magnetic sensor part which outputs a sensor signal based on a change of a magnetic field in association with the rotation of the magnet
Implementation Method 2
a closed magnetic field where lines of magnetic flux are oriented to be aligned in the radial direction is formed in the space interposed by the two magnets
Data Source
AI summary
A rotation angle sensing device is provided with a magnet that has a component with a magnetization vector in a direction orthogonal to a rotary shaft, a magnetic sensor part that outputs a sensor signal, and a rotation angle sensing part that detects a rotation angle of a rotating body based upon the sensor signal; the magnet has first and second surfaces substantially orthogonal to the rotary shaft, and a concave side surface that is continuous throughout all circumferences in the circumferential direction; the magnetic sensor part is placed within the space surrounded by the concave side surface, and at a position where an amplitude of a magnetic field intensity Hr and an amplitude of a magnetic field intensity Hθ on the virtual plane are substantially identical to each other, and outputs either the magnetic field intensity Hr or the magnetic field intensity Hθ as the sensor signal.