Rotating Angle Sensor Radial Flux Detection
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Solution Overview
Problem
Conventional rotating angle detecting sensors using columnar permanent magnets suffer from angle detection errors due to decentering and magnetic flux density changes, particularly when the magnetic sensors are positioned in regions with sharp magnetic flux density gradients.
Innovation Solution
The solution involves arranging magnetic sensors to detect radial magnetic flux densities in a columnar permanent magnet at positions with moderate inclinations in the small-diameter region, avoiding narrow gaps between the sensors and the magnet, and using a ferrite or alnico magnet with specific dimensions to minimize angle detection errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic sensors are arranged at positions with large absolute magnetic flux density (axial region), then the gap between sensor and magnet can be minimized, but angle detection error increases due to sharp magnetic flux density gradients
Solution Approach 1:
The patent transitions from detecting axial magnetic flux density (one-dimensional arrangement along the axis) to detecting radial magnetic flux density (arrangement in radial direction). This dimensional change allows sensors to be positioned in regions with moderate flux density gradients while maintaining sufficient gap distance, thereby improving angle detection accuracy without minimizing the gap.
Solution Approach 2:
The patent identifies specific radial regions with moderate magnetic flux density gradients and positions sensors locally in these optimal zones. By making the magnetic flux density distribution characteristics the basis for local sensor placement, the system achieves accurate angle detection while maintaining appropriate sensor-magnet spacing.
2Ease of manufacture
If decentering occurs between the permanent magnet center and sensor arrangement center, then manufacturing and assembly become more flexible, but angle detection error increases due to sensors entering diametric regions with sharp magnetic flux density changes
Solution Approach 1:
The patent anticipates potential decentering by designing the sensor arrangement to operate in radial regions with moderate magnetic flux density gradients. This pre-cushioning approach ensures that even when decentering occurs, sensors remain in regions where angle detection accuracy is maintained, effectively compensating for assembly variations before they cause errors.
3Ease of manufacture
If a columnar permanent magnet with uniform material is used, then manufacturing is simplified, but angle detection errors occur due to magnetic flux density distribution characteristics
Solution Approach 1:
The patent changes the detection parameter from axial magnetic flux density to radial magnetic flux density. This parameter change allows the use of simple columnar magnets with uniform material while achieving accurate angle detection by utilizing the radial flux density distribution characteristics that provide moderate gradients in specific regions.
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 effectively prevents angle detection errors by optimizing sensor placement and magnet design, ensuring accurate angle detection even with decentering and inclination, while maintaining a sufficient gap between sensors and the magnet.
Implementation Method 1
a curve representing a radial magnetic flux density distribution on an arbitrary plane including the center line of the permanent magnet has peaks (absolute values) at two positions
Implementation Method 2
The plurality of magnetic sensors are arranged to detect radial magnetic flux densities
Data Source
AI summary
An angle detection error is prevented by using a columnar permanent magnet that is radially double-pole-magnetized as a rotating angle detecting sensor while preventing a gap between a plurality of magnetic sensors and an end face of the permanent magnet from being narrowed. The permanent magnet is a ferrite magnet or an alnico magnet having a diameter of 4 mm to 20 mm, and an axial length of 3 mm to 5 mm. The plurality of magnetic sensors detects radial magnetic flux densities at positions axially spaced 0.5 mm to 3.0 mm apart from a central portion of the permanent magnet, the central portion having a diameter equal to or smaller than 20% of the magnet diameter to make it possible to perform detection in a range in which a distribution curve of a radial magnetic flux density has a moderate inclination.